The number and the fact that 2003 sucks slightly less than 2000. 🙂
In all seriousness, that’s quite an answer you’re looking for. But you should really try searching on Google first. For example, I found this site with a casual (and badly-constructed, I admit) search on the Goog:
One thing I really liked, especially for enterprise-class installations, is the fact that when you reboot the server, you *must* enter a reason. This is great for audit/tracking purposes.