I just don't get it. I understand that Twitter allows you to keep a "micro-blog", where each entry can only be 140 characters. I also understand that you can see what your friends are doing, when they enter their "tweets"
If I wanted to post everything, the entries would be "home", "at work", "fixing bugs", "reading email", "working on documentation", "in a meeting". These are all things can can be communicated though IM status messages. Also, I am sure that most of my friends would have similar status messages.
I am going to Twitter a fair try. I have configured Twitter to accept messages from my IM account, and my cell phone. Also I have installed Twitterbar, to make it easy to post tweets from Firefox.
If you are interested, here is my twitter profile, though I can't guarantee how much I will be updating it.