I'd rather have the Surface Pro. There are things I've wanted to try for a while on a touchscreen that would be easy to do on the Pro because it can run all the software that's already out there. If I got an RT tablet I would have to wait for someone to write an RT app that does the same thing and there's little hope it'll ever happen.
I don't see much happening with RT any time soon when it comes to being able to anything other than content consumption. If you want to get anything done you still need "real" Windows.
I'll have to wait for good reviews and detailed specs to see if it's a good ultrabook as well as a tablet. I'm concerned about the low amount of RAM it has and whether the onboard sound works well with ASIO4ALL.