ReSharper is a great tool, personally I think it is well worth the licence as you save allot of time. It has tones of features that aren't available in VS 2005 or are better/faster than the VS 2005 ones. Get the 30 evaluation licence and you'll see for yourself.
I'd recommend that you get the latest version from the Early Access Program (EAP) http://www.jetbrains.net/confluence/display/ReSharper/Nightly+Builds
We've move onto VS2008 since .Net 3.5 went go-live licence. ReSharper 3.2 supporst both VS2005 and VS2008 but doesn't support the new C#3.0 language syntax changes this is due in version 4 which is due out in Beta shortly. I've got all our developers using it since I moved to Aurion (Feb 2006) and I think they'd agree that it's a great tool.
I'd also recommend reading the ReSharper blog http://blogs.jetbrains.com/dotnet/ and the JetBrain's Ilya Ryzhenkov blog http://resharper.blogspot.com/
Damien