I installed the 5536 build of Windows Vista on my Toshiba Portégé M200 Tablet PC just the other day. One thing I noticed almost straight away was that in the Appearance Settings dialog Windows Aero was not only available but actually worked.
The M200 has a way below-spec graphics card to run Aero Glass only 32MB of on-board memory and a DX8 part. In previous builds it would simply revert back to the basic theme. Not in this build, I don't know if this is a bug or if Microsoft have perhaps re-considered outright disabling Aero Glass.
It does run slow with a few windows open, the Flip 3D feature is more of a slideshow on this hardware, but the live window previews and the glass itself run ok with just a couple of windows open.
But it does actually work. Obviously this may change in the next build, Release Candidate 1 due in a couple of weeks. But I like it and at the moment I'm running my Tablet PC with it turned on despite the slowdown with quite a few windows open. So hopefully this is a decision to allow Aero Glass to be turned on even on non-supported hardware.