I finally have installed ArcGIS9.4 Beta 2. The install required uninstalling my functioning 9.3, and that wasn’t as easy as other deinstallations. At first, I came across the same issue Jithen Singh describes, i.e. ArcGIS uninstaller stumbles over itself. Ignoring that, still left me with what seemed like a complete installation. So I simply deleted all the files and directories, and wiped the registry clean manually. Kind of strange that this wouldn’t be more straight forward.
For licensing of 9.4, check the ESRI site, here.
Anyway, it’s running, and I like the new look: