No matter how you slice, tablets were designed for consumption. The new UI owes itself heavily for consumption, but an office desktop is designed to produce. This is like a kick in the butt for productivity.
To roll back time to the last time Microsoft decided to combine some of their OS lines:
Years back MS decided that the distinction in their codebase for workstation and server was superflourous (except their High Performance Computing line). Standard Windows Server now shares the same codebase as the desktop version, just with a few extra doodads and a few things unlocked.
fast forward to today. I've seen such wonderful things as adobe reader 7 installed on Windows Servers. And what's that? Why is Windows Update telling me that there is a bugfix for Silverlight on server 2008?
I don't really think that Microsoft is aiming for businesses with this though, I think that they're trying to get a much more broader audience with the general population. They seem to be leaning much more towards the entertainment industry.