Last fall, I wrote about Microsoft's private beta version of Office 365 twice, first in a general overview and then with some hands-on impressions. Since then, I've continued using this eagerly awaited service and feel that I've really plumbed the depths of what's possible there. And this week, everyone can join in: Microsoft has now opened up Office 365 as a public beta.

Office 365, in case you've forgotten, is Microsoft's upcoming replacement for the Business Productivity Online Suite (BPOS), which features Microsoft-hosted versions of Exchange, SharePoint, and now Lync. But Office 365 will include a number of important improvements over BPOS—improvements that I think will put this service over the top and really establish Microsoft as the leader in online productivity. First, it includes hosted versions of the latest versions of Microsoft's server software; so we're talking Exchange 2010, SharePoint 2010, Lync 2010, and all the awesome new capabilities that come along for the ride.

Second, where BPOS was aimed very clearly at the upper end of the market and specified a minimum number of client licenses, Office 365 is for everyone. Literally. You as an individual could start up an Office 365 account for a relatively low monthly fee and see what all the fuss is about with Microsoft's leading edge servers. It's affordable to small businesses, too, providing all the benefits of an IT infrastructure with none of the costs or complexity. And Office 365 continues the BPOS mission as well, serving medium-sized businesses and enterprises with a variety of offerings (including the ability to mix and match client types), subscription-based access to the client-side Office 2010 Professional Plus application suite, and true domain and identity federation capabilities. This is the real deal.

Did I mention it was in a public beta? It is, and you should go check it out.

Broadly speaking, there are two types of Office 365 offerings: Small Business (which is also fine for individuals) and Enterprise (for those businesses with more than 25 users and more advanced needs). But it's actually a bit more nuanced than that, and there are actually other offerings—for kiosk workers (web only) and education, for example—as well as a set of Enterprise-based plans, each of which offers more capabilities as you move up the price-per-user-per-month scale.

And again, you can mix and match. So an enterprise may have some mix of kiosk users, plan E1 users (25GB of email storage, AD integration, on-site server federation), E2 users (adds Office Web Apps), E3 users (adds Office 2010 Professional Plus) and E4 users (adds enterprise voice services).

The cheapest plan, the one that an individual might consider, is $6 per user per month. That works out to $72 a year per user, or about $20 more than Google's paid Google Apps service. That's a bit more of a difference than I'd like to see, but Microsoft argues, correctly, that its offering is far more comprehensive and feature-rich.

How so, you ask? First, you can get anywhere/anytime access to real Exchange and SharePoint 2010 with this plan. That means via Office 2007 or 2010 PC clients—though you'll have to supply that yourself—or rich, web-based clients that many will find to be virtually indistinguishable from the PC clients. It means mobile access from a variety of Exchange ActiveSync (EAS)-compatible mobile devices—iPhone, iPad, Android, Windows Phone, and so on—along with EAS policies so you can ensure that your employees adhere to certain security needs, like remote wipe (if the device is lost or stolen) or a logon passcode with auto-lock.

Microsoft also offers a 99.9 percent uptime guarantee that is financially backed, meaning that if the software giant doesn't meet this standard, you get a refund for the downtime.

From there, the plans go up, both in cost and in capabilities. I've been testing the Enterprise version of Office 365 since last fall and will begin experimenting with the Small Business version now that the public beta is available. But I've found it to be a compelling alternative to on-site infrastructure and have successfully set up my own mini test company through the service, complete with email, EAS policies, SharePoint team sites and document libraries, and rich communications capabilities through Lync. It's an impressive solution.

So impressive, in fact, that my co-author, Rafael Rivera, and I will be using it to collaborate on and write our next book, Windows 8 Secrets. We're both impressed by the deep collaboration features in SharePoint in particular, and the ability to collection information, share it, and then write side-by-side, literally, in the same document. It's going to change the way we work going forward.

Your needs and experiences will differ, of course, but based on my time with Office 365, I see this as a revolution of sorts for smaller businesses in particular because it really provides them with a way to bridge the technical gap between their needs and their inability to afford or handle a complex on-premises IT infrastructure. And this is arguably one of Microsoft's core strengths: The democratization of technology.

But again, don't take my word for it. Office 365 is available now, in public beta form. Check it out. I suspect it will make many of you rethink your approach to providing these critical services within your own companies. And it will almost certainly garner some excitement with individuals as well.

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