I read on Voidspace about Better Gmail and figured I'd give it a try. It fixes one of the things I dislike about Gmail: lack of fixed width font on messages. I've gotten used to or around the other things I'm not wildly excited about, but lack of fixed width font when viewing messages is such a pain in the ass. Bugzilla emails come in and they're all screwy, emails from my stock broker come in and they're all screwy, emails from other people that involve text-based tables... they're all screwy, too.
Anyhow, Better Gmail has a Fixed Font option and it's awesome. I don't understand why the Gmail folks haven't added a fixed width font option to Gmail yet.