You haven't used Twitter or even seen it - you're just against it because it's mainstream? That's not a valid reason for rejecting something.
Just because something is popular with the masses doesn't make it automatically bad, evil, or lame. Following a trend just because it's popular and rejecting a trend just because it's popular are two sides of the same coin - they're both just reactionary.
Some people find Twitter useful. Some people don't. Either way is fine, as long as you've checked it out for yourself and made your decision based on personal experience and thoughtful consideration rather than just being reactionary.
Shannon, Chris, Nitin, Kirsten, Mad Max, Sbushfan11, Kai, myself and a million other people have tried it and found it useful.
LiL_NuKeY, Jake, Sean, Hidre, Eric and many other people have tried it and abandoned it. The rest of the planet has never tried it, probably doesn't know what it is, and is getting along just fine without.
You have to try it for yourself and find out. Or maybe you just don't want to try it at all, that's cool too. Just, please, don't act like your looking for input from others when you're really only looking to validate your own opinion.
It's also good for just saying random thoughts you have that for some reason you just have to share with your friends. It's not a big important statement just maybe something that struck you as funny or thought provoking.
You can tweet from your computer or your mobile phone which was the main emphasis originally so you could update and send pics from where ever you are.