My major use case, mail from my disconnected laptop, doesn't exist anymore. That laptop's battery failed, and Linux doesn't support the wireless card on my current laptop, and maildir, which offlineimap wants, is super slow on OS X, and searching in mutt is crap (mairix?), and these days when I'm away from an internet wire I want to be away from email as well.
One more and: in general, it's one less thing for me to manage and worry about.
(Unfortunately they screwed the pooch on threading (yes, jwz's document has been bandied about) and so all LJ comments end up in one thread. But things couldn't just work for me 'cause these are computers and I hate them.)