By now, if you haven't been scared off of running Vista Beta 1, nothing will scare you, so I might as well share this: the Tablet PC Experience Pack won't install on Vista Beta 1 either. I actually reported this to the responsible team a while back, but haven't been able to tell you til Vista Beta 1 was released publicly.
There are other avenues of app compat pain too - I installed a release candidate Vista at home and couldn't install Asheron's Call Throne of Destiny because it looks for "IE6 and later". Well guess what, we're moving on to IE7, so Turbine had better update their install logic, or we will have to implement a compatibility hack similar to the one used for drivers and other executables.
If this keeps up, Windows will just be an environment that runs Virtual PCs. We'll have Petahertz CPUs with Petabyte storage, in a package that you can clip to a lanyard (a la WMA players) all just so that we can run Virtual PCs hosting old Windows.
Sometimes I crack myself up...
(update 8/2/05: fixed typo "Petabye" (sic) and removed "Windows" from title)