Great to hear ....
Like they always says, convert them to use cross-platform applications to use if you can't have them convert to underlying OS yet such as web browsers and office applications. Once they are familiar with OSS applications on Windows, it's a lot more easier to change underlying OS since most users don't give a crap about what OS they are on.
I use OOo extensively to run my small business ( and Win2k with Office Pro 2K on one box just for the sake of compartibility with my partner large head office ). I KNOW that OOo is a lot more superior in terms of stability and usefulness. Or that I tend to change my computing behavior to suite the program I'm being used than to bitch about how it's not the same as OTHER office programs. I guess.
Good luck with your endeavor.