It's become such a part of my day to day life that I can't really describe the things I was missing before. The best things about it are probably the strong, flexible security and ease of administration. It also gives you everything you need from a small shop all the way up to a globally available decentralized data store.
There seems to be a good comparison here [tu-chemnitz.de]. I would strongly recommend AFS for all of your distributed filesystem needs. (The OpenAFS developers are cool too!)