Today at its first user conference (see our live blog here, or see the announcements on Box’s blog) Box made several announcements, most notably a new enterprise grade version called Box Sync.

Box CEO Aaron Levie also talked up new security features, the ability to pipe Box updates into Salesforce.com Chatter and partnerships to preload Box on Motorola Xoom devices (Box is already preloaded on Samsung devices) and on HP desktops sold to SMBs. TechCrunch reported today that Box also landed $50 million round of funding lead by Salesforce.com – a round that quickly follows its $35 million round in July and the $48 million in February this year. Update: Levie told me in an interview today that the number TechCrunch reported today is inaccurate, but is in the ball park.

But sync is Box’s killer app. Security and social are table stakes. Sync is unique and very difficult to get right. And Box has been getting it right. Rumor has it Box turned down an acquisition offer of over $500 million. What would a potential acquirer want from Box? My guess is Box’s synchronization technology, which is getting better.

The typical synchronization service – like Dropbox, SugarSync or (up to now) Box – syncs files between a single users’ computer and their mobile devices. Box is moving beyond individual users, and allowing teams to have folders that sync across users’ desktops and devices. So a marketing team could have a shared folder that syncs between each team members’ desktop, the cloud and all their mobile devices. They can also add outside users, such as clients, to the mix.

Services Angle

Box bought an in-browser document editing company called Increo Solutions in 2009, and has long positioned itself as an alternative to Microsoft SharePoint. But earlier this year it added integrations with Google Docs, allowing users to edit files in Google Docs and store them in Box. Prior to that it announced an integration with SharePoint and other enterprise content management systems, and played up the ability for Box to act as a connector between Google Docs and SharePoint or other ECMs. That seemed like a big change for the company.

But the truth is, it’s tough to compete with Google Docs, Microsoft and Zoho as an Web-based office suite, and it’s hard to compete with established enterprise products like SharePoint, Documentum and Alfresco. By doubling down on sync and making documents available anywhere – an ECM server behind the firewall, in Google Docs, on a local desktop, on a smartphone or tablet (even when you don’t have a signal) and on Box itself, Box is making itself truly useful and unique.

Here’s what Levie told me earlier this year when I asked him about Box’s new direction:

“Ultimately, our focus at Box is to provide the best way to share, manage, and access information in the cloud — and we want to enable customers to interact with the content stored on Box in a variety of ways, many of which are provided through partnerships and integrations with our platforms,” he replied. “So while we’ll continue to focus on our own editing and collaboration features, we also want to connect to the applications our customers interact with heavily, and that means working with leading online office applications, like Google Docs.”

Disclosure: Motorola announced it will give free Xooms to attendees. I’m not yet sure if the press are getting them as well.