Our shop has XP as our standard OS. Instead of moving to Windows 7 directly, I suggested we use Ubuntu 10.4 as our base OS, and we make a Windows 7 VM. This not only gives us flexibility in what our clients run, our legacy guys can use Ubuntu to web surfing and email, and use XP/Windows7 for legacy development.
I am impressed with Ubuntu. It found our network during install and was ready to go. Most of the packages do not need a command line, and updates work just like Windows. The thing that caught my attention though was the Windows 7 "wait" circle looks shockingly like Ubuntu's "wait" circle!