I got an error trying to install IE 7 Beta 3 on Vista Beta 2 Build 5384. The installer said - "Your operating system is not supported by this package."
Kinda funny ... [UPDATE: I'm a dork ... I tried to install the Windows XP version on Vista. Duh!]
BTW ... Vista Beta 2 Build 5384 and Office System Beta 2 Kit 2007 (both from MSDN) are installed on my Toshiba M4 Tablet PC. So far I've enjoyed the new UI changes with Word and with Outlook.
The UI changes in Visita are nice and flashy. Tablet functions are even more impressive after about 1 hour of moving around and just doing standard stuff. No OneNote testing yet.