Much was said in recent days and weeks about Research In Motion’s BlackBerry PlayBook, but that was based on the pre-launch software, which was updated yet again on the April 19 launch date. We can expect extremely frequent further updates to the PlayBook software for the foreseeable future — for all I know, almost every day.

The bottom line is this: If you are a BlackBerry user, the PlayBook will serve you very well already today even though it still lacks many important apps. If you are not a BlackBerry user, the PlayBook is probably not for you until closer to the middle of 2011 when the software becomes available that eliminates the need to optimize the experience together with a BlackBerry.

From a financial perspective, RIM can sell the PlayBook into its own installed base of about 60 million BlackBerry devices, as well as the broader market. It is anybody’s guess as to how many of these 60 million users will add a PlayBook, and, of course, the swing factor is even greater in terms of addressing the broader market of billions of cell phone and PC users. My own estimate is that RIM should be able to sell at least 4 million units per year, with plenty of upside potential in 2012.

In terms of the initial sell-in, RIM has distributed PlayBook devices to some 20,000 retail outlets, as well as online sales. One might surmise that the initial channel fill would be at least 30 units per store, plus some number for online sales. It seems reasonable that the initial channel fill is close to 1 million units. Assuming an ASP of $400, that would mean $400 million in May quarter revenue, probably at a low gross margin. This is for a company which did $5.6 billion in revenue in the last quarter, which grew 36% year over year.

Let’s go over the pluses and minuses of the PlayBook:

Out of the box experience: Very competitive with the best from Apple(AAPL) and Android from Google(GOOG). No need to plug it into a PC, although that’s optional and can yield some additional flexibility. The box includes a cushioned sleeve, which can carry you over until you have decided which one will serve your longer-term needs. Hard-core BlackBerry users have tended to buy very durable cases from companies such as privately held Otterbox.

Hardware: The 7-inch 16:9 aspect ratio tablet has an excellent 600 x 1024 display and has a quality feel better than the Motorola(MMI) Xoom and overall on par with the iPad. Unlike any of the Android tablets, the PlayBook’s MicroUSB charger can also charge almost any smartphone from not only BlackBerry, but also Motorola, HTC, Sony Ericsson, LG, Samsung, DellM and others — except Apple, of course. This ought to be a solid sales argument for the PlayBook. Battery life appears solid at close to eight hours.

Operating system: The overall operating environment has what may be the best interface of any tablet available in the market today. In comparison to the iPad, the PlayBook allows for better multitasking and more useful gestures. One also has evolved away from that infinite grid of mono-form app icons. In comparison with Android 3.0 Honeycomb, the PlayBook is a lot less confusing and much easier on the eye. I guess you could say that the PlayBook looks a little bit more like the iPad and has its ease of use, but has the fundamental capabilities of Android 3.0 Honeycomb. As far as I can envision, that’s probably the best combination in the market right now.

Browser: Its capability to render Flash content sets it apart from the iPad, and at least for the time being appears to do a better job than Android. Still, there is a lot to be fixed with respect to page load times and overall finesse. Despite its natural handicap, the iPad browser is more mature and just works a little bit better, aside from its lack of Flash, which can be a prohibitive handicap for some people. iPad has the advantage for now, but PlayBook has laid the groundwork to race ahead in the coming months.

Email and other core apps: In its current version, the PlayBook offers native email, address book, calendar and some other basic PIM apps only for those who connect via Bluetooth to a regular BlackBerry smartphone. For those of you who fulfill this basic requirement, this works extremely well and has crucial benefits.

For example, this so-called BlackBerry “Bridge” effectively gives the user free cellular connectivity to the PlayBook. Apple’s iPad and Google’s Android devices will cost you at least $20 to $30 or so per month for this kind of functionality. This is a significant advantage over the competition.

The other “Bridge” advantage is security. If you lose your PlayBook, no personal information such as emails, address book or calendar will be compromised. This even includes cases where a child runs away with the tablet inside the house, or if you want to lend your PlayBook to someone even sitting across the dinner table — just terminate the Bluetooth session and you’re safe to go. It cannot be emphasized enough how useful this is, and this plays right into the hands of enterprises who need to minimize security risks and other snafus.

Overall app selection: As of this writing (April 19), very poor. Almost none of the apps I normally use on my iPad are available on the PlayBook. Obviously, the superior browser makes up for some of this, but there is still a wide gap. Important and popular apps ranging from Skype to Facebook are not available. Not all of these can be perfectly replicated inside the browser, even though the PlayBook may be the first tablet to challenge the need for having too many apps. Keep in mind that when the iPhone was first released in 2007, it took one year for any apps to appear at all, so RIM is moving faster now and could have more than 300,000 apps by the end of 2011, thanks in part to the de-facto app compatibility with Android. This clearly is RIM’s major challenge with this platform — quantity and quality of apps. It started the race April 19 way behind the competition.

Competition against the Apple ecosystem: This is a huge challenge for RIM. It’s not just the comprehensive availability of content and software modules inside iTunes. It’s also Apple’s integration between its iOS devices — including Apple TV — and the Mac, such as FaceTime and AirPlay. It will be very hard to win over people who have already taken advantage of these integrated features inside the Apple ecosystem. RIM must broaden its portfolio and catch up on these important cross-device functionalities.

Competition against Google’s Android ecosystem: This one may be easier than the Apple challenge. Native apps for Google Docs, Google Voice, Google Talk, Google Reader and others need to become available, just like they mostly are for the BlackBerry itself. The biggest long-term threat from Google will not be Android, however, but rather Chrome OS, which will first launch in traditional PC form factors but then likely make its way into tablets and finally also smartphones, probably by 2013 or so.

It is clear that the initial version of the PlayBook is very much focused on the businessperson’s need. Serious businesspeople who have to engage in proper and frequent business communications typically have a BlackBerry, and it allows for the secure and economically efficient Bluetooth tethering to the PlayBook.

The traveling businessperson will also notice another advantage over the iPad, and I’m not talking about the standards-based battery charger. Apple has repeatedly made clear that apps related to adult video will not be allowed on the iPad. Even those who want to access adult content via the iPad browser, are met with obstacles resulting from the servers identifying the iPad as such, and re-routing the user to Web pages that extract payments for content that is normally free when accessed from a regular PC.

In contrast, the PlayBook has a browser that fulfills the traveling businessperson’s entertainment needs. Adobe Flash compatibility in conjunction with the fact that the browser accesses adult Web sites in a manner similar to a regular PC web browser means that all content is available, and that so much of it is also available for free. RIM knows how to cater to America’s traveling businesspeople, and how to minimize the cost of accessing vital information — no longer restricted to confidential and classified email communications.

The PlayBook’s business focus is clear: The PlayBook offers secure and efficient email access, fits in many suits, and offers the businessperson unrestricted Adobe Flash-based adult video while on the road — on all fronts better than the competition. It looks to me like RIM has carved out a strong focused businessperson’s niche here.

What are the next steps for the PlayBook? Here is what you should expect:

Constant bug fixes to improve app stability and various use cases. These updates could end up being made available almost every other day for the rest of the year. As a user, you will feel like you’re in some form of “beta mode” for the next six months or more — just like Google likes to describe many of its products for several years even after tens of millions of people have adopted them.

Much more and higher-quality apps available. This is the most important focus for the platform. By the end of 2011, count on well more than 300,000 apps, which would put it on par with — or ahead of — Android and iOS. Obviously, the main reason for this large number will be that the PlayBook will likely be able to run Android itself, on top of all the other forms of apps (Adobe, Java, native, etc.).

Un-tethering the core PIM apps (email, address book, calendar, etc.) from the BlackBerry so that they are native to the device and you can choose to tether to an Android or iPhone.

HSPA, LTE and WiMax versions for users to simplify the fastest and most ubiquitous connectivity, even though it is more expensive than tethering.

One or two larger versions, such as a 10-inch version. I have said for a long time that serious tablet makers should have four sizes to meet most market needs: 7-, 9-, 11- and 13-inch models.

It appears clear to me that RIM will be able to round out these software and hardware evolutions during various stages between now and the end of 2011. At that point, it looks to me like RIM will be competing successfully in the tablet marketplace, with Apple probably in the lead, Android likely a distant No. 2, and RIM and Hewlett-Packard(HPQ) both gunning for Android. Once we enter 2013, however, I would not be surprised to see Google’s other OS — Chrome — enter the market as the formidable force. That Chrome OS will ultimately be RIM’s biggest challenge with the PlayBook — not the iPad.

[Cross-posted at The Street]