…as just discussed with Russell in the Crown and Sceptre,
“World of Warcraft for those who can’t be bothered with all that elf crap and fighting, rendered in Haiku…”, “Part reality-tv, part improv, part microblogging”
It’s decidedly playful – with the constraints of the medium and the unashamed mundanity of most of the content only adding to the fun.
The explicit ‘reporting’ nature of it seems to make it more attractive to me than perhaps some other things that might be similarly classed as ‘self-surveillance infotainment’ like Plazes or Jaiku.
Whilst it’s definitely ‘having a moment’ – it’ll be interesting to see whether it settles into a pattern of the same sustained interest and fun as Flickr, or move into the realms of YAZSNS (Yet Another Zombie Social Network Service) full of tiny 160 character ASCII tumbleweed…
Petafloptimism 
I think it might last. The accretion of ASCI moments adds up to something you feel you’d like to keep. And keep up. It feels like digital ephemera, like collecting all your bus tickets.
It might last and I am enjoying it http://www.twitter.com/jah/ but I have wanted to respond to someone’s Twitter text and so it’s not branching except unless you subtly work in your feelings into 160 characters or address your reply to only one friend while all your other friends read it?
It’s simple, elegant, and it makes me want to expand its use and role in my life. It also makes my phone chew battery and chirp when I’m not really wanted, except to watch my friends think pithily. Which is an attractive concept for cosmopolitan nerds with short cycles to describe their lives. Blogging takes too much time. Especially with a screenshot! Nice one Matt Jones.
I introduced this to a couple of friends who used to have 2 level conversations on Google Messenger, one via the main chat window privately with each other, then a more public one via their status messages.
They love it.