Desktop Windows does, but stock windows apps generally don't work well in tablet mode without adaptation. Metro (in the form of Windows Phone 7) is lagging. Windows 8 seems to be something like the two of them running on the same kernel, but unless there are apps on both "sides" that synergize well, the whole may be less than the sum of its parts.
The intel version at least will be able to run all apps- and the keyboard has a multitouch trackpad.
UIs will need to change, for sure. But as long as it's possible to port large portions of the codebase of existing Windows apps (see the demo of Lightroom they showed), there should be a lot of options.
The RT version reminds me of the PC Junior, with its chiclet keyboard, and has no legacy apps. You're right about the Pro version, but it seems to me that's designed for people who need a laptop. Those people will buy a laptop.
Are you suggesting that Windows doesn't have an ecosystem?