Wow, I love the simplicity that ZooKeeper brings to a really hard set of distributed problems. Check out this Introductory Video that explains it more in depth. Basically group leadership/coordination and cluster wide configuration issues are taken care of if you Use ZooKeeper.
Oh and it’s an Apache Project now. Yay! Seems like the project website is still not fully setup since they are migrating from SourceForge to Apache, be here’s a link to the source tree.