I don't think it's in wide practice, but I'm a huge fan of an idea that Douglas Coupland put forth in "Microserfs": Every member of the team uses a different operating system, so you're always portable (and if there's a problem, you know immediately).
Just what I always say. If you create a project thats suppost to be multi-platform you need to live that. Stop using "outdated" single platform software, thats just not the future. It's like not knowing English and beeing a programmer. It just doesn't work in the long run.