The guys at CodingMonkeys have just announced the release of SubEthaEdit 2.0
It looks basically the same (after a 30-second tryout), but has code completion, and the ability to invite folks to a shared document.
Looks like a good release (more info here: SubEthaEdit - Features), but it's got a new network protocol which isn't compatible with 1.0 - so everyone has to upgrade. So, go upgrade! ;-)