I love good commit messages as well, but it can be hard to convince people to write them. I always hear "Why? i don't use them" which is self propelling. You don't have good messages, so you don't read them when you want to know something, so you don't write good commit messages.
Another thing I like to put in commit messages is the ticket# (of what ever bug tracker you're using) of the feature/bug task that drove the change.
I don't really do comments all that often (generally, only for "Chesterton's fence-esque" things) but I do really rely on good commit messages. They are really helpful when going back in history and trying to get a general idea why something changed.