It's not compatibility reasons I'm concerned about, it's all the new annoyances Microsoft put into SP2. There are always a few people out there who get upset over everything, or there's other people whom I'm just starting to do business with, and I just don't want to be the one to tell them "yes, I just made running files & navigating the internet super annoying to use."
Eventually I'll get SP2 on all computers, I just want to first really go through & learn how all the new features work & also how to turn them off (especially how IE handles pop-ups, activex installs, and file downloads). But for now SP2 is not a priority for me, I've got a lot of other work that needs to be done first.