I have and got the Pro edition because it contains XP compatibility mode.
I would do, but the new version of Virtual PC (which forms the basis of that) seems to require that the CPU has hadrware Virtualisation Support such as Intel VT-x or AMD-V however my CPU doesnt have that (its a CoreDuo laptop) which is annoying.
When windows 7 comes out, i would never consider going back to XP or Vista for new builds but i would hold out on upgrading my vista machines for a while due to cost. XP machines would definately be upgraded if they could handle it.
Then again , the EU version of windows 7 looks to be utter shit. Comes with no IE or Media player or anything, and limited upgrade facilities. (due to ms fighting with the courts over anti-monopoly laws)