So far I’ve got to give a big Meh to Google Buzz. I imagine they’ve got more up there sleeve than it appears now, but so far it appears to be a much much slower, less functional version of FriendFeed.
FriendFeed is fast and does a great job with comments and ad hoc groups and pulling in outside content (blogs, pictures, etc). The drawback is that none of my friends use it so it doesn’t feed me anything. I also like its one-way friend model, like a Twitter follower.
Facebook is way too heavyweight and too closed, with all of the content contained inside the Facebook ecosystem. But everybody uses it so if you’re trying to communicate with people it’s pretty much the only game in town (at least with my friends).