I just jointed Twitter after reading a post from Joi Ito. I added my first update, but i'm not 100% sure the web interface is particularly great - i do like the idea of mobile use tho'. We only one or two friends it's not hugely useful but with a network of friends it may get pretty interesting.
I'd like it mashed up with Plazes maybe - what are you doing and where?
btw, if you haven't tried Swivel yet and like stats, it's worth a go!