I agreed with Mat that Microsoft is betting a lot on their keyboard-and-trackpad cover, but I disagree with this conclusion:
Because if Microsoft can solve input with its super slim touch typing keyboard and case, then it will have pushed the tablet market forward again, and that’s always a good thing.
I don’t think the Surface keyboard covers are primarily about solving the typing-while-mobile issue. The keyboards are a necessary component because of the software.
The Surface for Windows 8 Pro runs full-on traditional Windows apps — apps which you cannot use with touch input. You need a keyboard and trackpad for those apps. The keyboard is just one (albeit a big one) component in Microsoft’s reach for all those would-be tablet users who still have a foot firmly placed in the PC camp.