I thought I was the only one that didn't "get" twitter.
I like the 256. It's computer-y and give just enough more room to make a complete thought without overly diverging from Twitter's 'thing.' (of course, with images and video and such... maybe they've blown that already!)
I do really like the ability to comment on a re-tweet though, so all their new ideas aren't bad.
But, I think Twitter's biggest challenge is that it's quickly becoming just a bunch of schedule-bots dumping content in. Once that saturates, everyone will stop reading them... the end.