I've been toying around with the CTP for a couple of days. There are some very nice stuff to see, and everything seems to be much smoother and faster (beside the setup, that is; I tried a clean install - which took over an hour - and an upgrade from Windows XP [first available in this CTP] - which took well over three hours...)
I have a very old display adapter (ATI Rage Fury Pro) which, in earlier builds, was able to run the DCM/DWM (but not very smoothly, naturally.) This time, the registry hacks to get the DWM ignore the incompatibility didn't work. So I ventured on a mission to find where they hid it this time. This is what I came up with (copy and paste into notepad and save as dwm.reg):
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\DWM]
"UseMachineCheck"=dword:00000000
After making this change, just open the task manager and kill dwm.exe. The service will restart itself, and if your adapter is good enough, you'll see Aero Glass. I haven't been thus fortunate myself, so I'll go ahead and buy a new adapter (which is long-due.) Note: if all you see is your desktop flickering like hell, hitting CTRL+ALT+F9 will temporarily disable DWM, and allow you to unsent that registry key (it's enough to change the UseMachineCheck value to 1.)
Other settings I found under the same key: Animations, AnimationsShiftKey, Blur, Composition, DisableDwmRotation, DisableDynamicShutdownUI, Schedule, ThreadPriority, UseAlternateButtons, UseDPIScaling (I'm assuming these are all DWORDS, but you should try and see.)