Twitter is its own thing. For some it's about attention, but for most it's about networking and information. For example, there is a Worldcon Twitter account. Now imagine 1000 fans on Twitter all following the Worldcon account. Aside from it being a good way to find other fans, anyone who wants a taste of what's going on at Worldcon can check out the followers list for Worldcon and see quick sound bites of things going on at Worldcon, from all over Worldcon. Because Twitter has a 140 character limit and is ideal for phone usage, people are far more likely to be both succinct and post more often, making for an amazing live feed. There are many other uses, but suffice it to say Twitter is it's own beast and is still evolving and has already evolved more than LJ, Facebook, MySpace, etc. It's quite fascinating really. Worth trying out IMO.