The whole market for Surface is people who want the convenience and small form factor of a tablet but who find an iPad not powerful enough to do all of the work they need to do (e.g. not having fully featured versions of Office).
I think the reviews sum up nicely the experience I have had with the Surface. On its own, not a good tablet replacement. On its own, not a good laptop replacement.
As a laptop the Surface is interesting, but not very usable. Unless you have it on a desk or table, the kickstand is not convenient for placing this thing on... well... your lap.
As a tablet it's heavy and not very comfortable to hold for longer periods of time. And its 16:9 ratio makes it very awkward to hold in portrait mode. It gets top heavy really quick because of its extra length.
It's a nice attempt by Microsoft, but I have a hard time believing that's it's enough. It really feels like another Zune project to me.