With the help of one of the ReSharper staff I installed ReSharper 3.0 beta onto VS 2005 Orcas March CTP. It worked very well in the environment.
Use this command on Vista from a command prompt window that has administrator priviliges:
msiexec /i resharpersetup.msi vsversion=9.0
msiexec /x resharpersetup.msi vsversion=9.0
I am waiting on the ReSharper release that will include the .NET 3.5 since so much of our application under development is dependent on the future release of .NET.
However if your development does not include .NET 3.5 or very few instances then by all means try this version.