Let’s say you could buy an Apple MacBook Air — but with twice the battery life, at half the price. Does that sound attractive?

Duh!

What is this — a so-called “ultrabook” that Intel is pushing through its usual OEMs? Nope. Ultrabooks may be slightly less expensive than a MacBook Air, but that’s par for the course for the usual multi-decade Microsoft-Apple comparison anyway. Nothing new there. Just predictable linear progression.

No, the laptop that will fit this bill is another new class of Microsoft-based product hitting the market simultaneously with the “regular” Windows 8 this October-November. And it’s not based on Intel or AMD.

Microsoft published a lot of details about this new class of laptop Feb. 9:

I thought that the world would quickly absorb this detailed description of Microsoft’s plans. However, in the two months that has passed, I find that few people have drawn any conclusions from Microsoft’s great revelation.

It’s all hiding in plain sight. Just read it.

Side by side with Windows 8 for Intel and AMD, Microsoft is making a version of Windows 8 available for use on devices using CPU/GPU SoCs (Systems-on-Chip) from Qualcomm, Nvidia and Texas Instruments. These will fit almost any “large” (i.e., non-handheld) form factor, including tablet, laptop and desktop. The focus is on tablets, laptops and “hybrid” laptops/tablets.

Just consider, for a moment, some of the key reasons the Apple iPad became so popular: Instant-on availability, great battery life, great security, easy manageability. Those attributes also apply to Windows 8 on ARM. Here’s the difference: It’s an unsuccessful struggle to make your iPad as productive as your laptop. People try all the time, but nobody has shown me that it can be done successfully, for a variety of software and hardware reasons that are not likely to be overcome anytime soon.

What’s the upside here?

1. Form factor: These new chips draw a lot less power and generate less heat than x86, so they don’t need a fan — just like your iPad doesn’t need a fan. This means they can be made thinner, lighter, fit a bigger battery and yield better battery life. Also: instant-on boot-up.

2. Cheaper: The chips are more inexpensive to buy, and the devices are cheaper to build. Expect $50 to $100 price savings compared with regular old Windows 7 PCs.

3. Simpler to manage and more secure: Applications either come pre-loaded (Microsoft Office) or only from the Microsoft app store. This is just like iOS or, of course, the current Windows Phone 7.5 — but unlike BlackBerry or Android, where you can side-load apps. And, of course, unlike Windows 7 PCs today, which remains the Wild West in terms of security and manageability.

What are the major drawbacks?

1. No app compatibility with Windows 7 (or 8) based on x86 processors. Intel makes a big deal of this because it is, of course, in its interest for this ARM version of Windows to have zero success. The argument is that “enterprise apps” won’t work on this new ARM-based Windows 8.

That’s true — for some. But what if all you need is Microsoft Office plus a browser? Then these new ARM-based PCs would be better for many users, compared with their x86 counterparts, built on Intel and AMD.

2. Gaming and external performance. It is unlikely to rival the larger, more discrete PC systems. But then again, this comparison may be unfair.

3. Outlook. Windows 8 on ARM will have Word, Excel and PowerPoint — but apparently not Outlook. Are these people serious? This omission sounds a lot like when BlackBerry launched its PlayBook tablet without email. If Outlook is not provided for Windows 8 on ARM, the whole thing looks like sabotage to me. For many users, enterprise in particular, Outlook remains the remaining reason to stick with a non-Google Chromebook PC/laptop platform. If Windows 8 on ARM lacks Outlook, it will remain a toy until it gets it. BlackBerry eventually added email to the PlayBook as well — after a one-year disaster.

People use Outlook because they have closer to 25,000 contacts than 250, and they need to organize these in an Excel-like format where columns need to be heavily customized for viewing and sorting in specialized manners. Any simpler implementation is a toy, unsuitable for serious contact databases.

That said, what will be the market impact of Windows 8 on ARM? There are two ways of looking at this:

1. Compared with a “regular” x86 Windows 8 laptop: Many users will prefer the ARM version because it will:

(a) Be thinner

(b) Be lighter

(c) Have better battery life

(d) Be more secure and easier to manage

(e) Be cheaper

(f) Have instant-on boot-up

Only people with particular legacy application needs, including gamers, will remain on x86 Windows 8. In addition, the same goes for Outlook users, assuming that issue isn’t remedied.

2. Compared with an Apple MacBook, pretty much the same as in (1), but with greater emphasis on price and perhaps less emphasis on security and manageability.

Here is the really big question for Windows 8 on ARM, aside from its “oops, let’s shoot ourselves in the foot” with the missing Outlook issue: If you buy the security and manageability argument, and you are happy with the compatibility between Google Docs/Drive and the Microsoft Office suite, why don’t you just take the full step and go with a Google Chromebook instead?

The answer may be found in a small number of more consumer-oriented applications rather than enterprise: iTunes and Skype, in particular. Many people require a Windows or Mac laptop because they need it to manage their iTunes podcasts, refreshing the update list every day. As for Skype, there are alternatives such as GoogleTalk, and you can also use Skype on a smartphone — but some people may not like those alternatives.

What about the stock impact? Let’s consider the following players:

1. Microsoft: Windows on ARM has great potential for Microsoft, enabling it to offer a kind of performance for productivity tools that Apple cannot. In addition, it basically punches Intel and AMD in the gut, more than doubling Microsoft’s silicon choices.

2. Qualcomm, Nvidia and Texas Instruments: All upside, no downside. This isn’t a question of “if.” It’s just a question of “how much.” Every unit sold comes straight out of the pocket of Intel and AMD.

3. Intel and AMD: See the mirror image of (2) above. All downside, no upside. The question is only “How much?”

4. Apple: Actually, same as Intel and AMD above. Incrementally, this strengthens Microsoft, and could either take market share from the Mac, or at least reduce the defections from Windows to Mac.

5. Google: Ambiguous. On the one hand, Windows 8 on ARM will reduce the propensity for people to defect to a Chromebook because the product is much more competitive than “regular” x86 Windows. On the other hand, Windows 8 on ARM may awaken the thought in individuals and corporations alike that “If we are going this far, why not go all the way?” … by getting a Chromebook? The software/management/security architecture behind Windows 8 on ARM is, however, a recognition that Google had it right with the Chromebook.

What’s the bottom line on Windows 8 on ARM? If Microsoft can just plug the “Outlook hole,” it has a huge winner on its hand, offering a product sliced very intelligently between, on the one hand, Windows 8 for x86 and Mac OS and, on the other, Google’s Chromebooks. If Microsoft drops the ball and doesn’t offer Outlook for Windows 8 on ARM, it will still be a plus for Microsoft and its new laptop CPU suppliers (Qualcomm, Nvidia and Texas Instruments), but not nearly as much upside as it would be if Outlook were available.

I expect both Windows 8 for x86 and Windows 8 for ARM to be available in U.S. retail starting around Oct. 31, plus or minus a few weeks — in numerous form factors ranging from tablets to laptops to desktops and various laptop/tablet hybrids.

[Cross-posted at The Street]