The only problem I could see is that the Airport software might not run. I know the Airport Extreme only officially supports XP and Vista, so it won't let me install the new version of the Airport software on my 2000 machine. If you have another computer to do the setup it works fine, though.
Short answer:
it should work, but you won't be able to do any admin on it from that machine. Which is a problem if it's your only machine (unless you know someone with the new Extreme, who can install the new software for you).