twitter is only good if you do not actually mention what you have been doing all day. it's boring. unless you lead a very exciting life.
twitter is good for recommendations
twitter is good for reading updates on fantasy scenarios involving putin and the cure
twitter is bad when someone you used to date who sent you an invite to a party a couple of weeks ago doesn't allow you to 'follow' them. and you humilate yourself because you realise twitter isn't just being crap and try to ADD THEM TWICE
twitter has a built in embarrassment factor that prevents you from updating too much so i'm not sure whether it's addictive yet (signs are good that it's not)