Surface has a single USB port and a mini HDMI cable input. Both of those things sound minor, but they make Surface a lot more useful than you might imagine. For part of my review period, I used a stock Bluetooth keyboard and mouse while Surface was connected to the large screen in my office. (By the way, no configuration was needed; it just worked.) And when I wanted to add documents to the Surface, I simply connected a standard USB hard drive and dragged and dropped. These are simple things that you can't do on an iPad or an Android tablet.
Surface is powered by the version of Windows 8 that it calls Windows RT, and that's the source of some of the strengths and the weaknesses of Surface. Windows RT runs on ARM processors, whereas Windows 8 runs on Intel processors. The great thing about ARM processors is that they give you phenomenal battery life. I easily was able to work for at least 10 hours per charge. But because you've left the old Wintel architecture behind, you can't run any legacy applications. In the Windows RT world, you are restricted to applications from Microsoft's store or Web-based applications. If you need to run legacy applications, you can either wait for Microsoft's Surface Pro, due later this year, or bypass Surface altogether and look for a PC that runs some version of Windows 8.
As I write this, Microsoft's application store is pretty sparsely stocked, but most of the table-stakes apps that many users use are there. Hulu and Netflix are available. Some Twitter clients are also in the store, but there's no native Twitter app. Also notably missing is a Facebook application, although the standard Facebook website works just fine on the Surface.
Flash support is limited and whitelisted on a site-by-site basis. Some sites worked flawlessly for me, but others did not work at all. This is another try-before-you-buy situation, especially if you rely on a site that's Flash-based.
What ultimately helps balance the application story for Surface is Microsoft Office. Every Surface comes with a built-in copy of Office that includes Word, Excel, PowerPoint and One Note. There's no Outlook (the native mail, calendar and people apps all work with Exchange). And this is no watered-down version of Office; with a few exceptions, all features are present and accounted for, and they work with the standard Windows desktop for file management and manipulation.