I use it all the time. It can easily run away from you once you get to following so many people that you can't read everything.
It's a great way to keep up with the latest updates with patches, new game announcements, and game deals (these sort of things can be very time sensitive).
I know a few VGC folks use Twitter, and we all use it differently, I think.
I mostly use it to keep up with gaming news (I don't visit any particular gaming site regularly) as it's a good way to get quick headlines and such. In regard to what I tweet, I use it for giving notice about any livestreaming I might be doing/planning and will retweet gaming news/deals that I like. I'll also post a silly pic here and there for friends.
www.twitter.com/desocietas