I've been thrilled see that Windows 7 would be compatible with GP 10 from Day 1. David has written about how he has also tested running GP 8, GP 9 with Windows 7.
Officially though, only GP 10 is supported with Windows 7. What I noticed in the System Requirements for GP 10 is that - "Integration Manager is currently not supported on Windows Server 2008 R2 or Windows 7."
That might be something to keep in mind before you start recommending Windows 7.