I already download it and played a little with it, looks OK so far but the uninstalling part was miserable:
uninstall beta 2 (some estrange error about MVC 2), reboot
uninstall .NET Framework version 4 Extended reboot,
uninstall .NET Framework version 4 Client reboot
manually delete some leftovers (ASP.NET MVC 2 and another one i cant remember)
then install VS2010 Ultimate RC:
Installing .Net Framework 4, reboot
Installing all the other components.
After that everything seems OK, UI is responsive and loads faster than beta 2.
Tomorrow at work i will test this puppy in our internal apps.