Just tested out Armory with Bitcoin 0.90rc2 (64bit) on a Windows 64bit machine. The only issue I had was that the binaries couldn't be found on the machine. I had to point Armory to the location of bitcoind after which it started working.
Does 0.9.0rc2 install to a non-standard location? It'd be good to have a heads-up that things like that are changing...