Yeah, I've still got one of them somewhere. I used it a lot and even took one to work. I had to keep a mouse plugged in so that if someone wanted to show me something on my PC they had something they could understand.
Great for CAD stuff.
But I did find it gave me a few problems, RSI wise, though I refused to accept it at the time.
For quite a while now I returned to a mouse and I use a Logitech G500s.
I don't find it that bad for what I do in which ever DAW I am using. I'm not doing major fader riding or anything like that. And most of the time I just use the scroll wheel for fader/knob adjustments.
Got one of these too, stuck in a box somewhere. Not used that one for ages... I think I just preferred the Microsoft one and, for a time, there wasn't another trackball like it. For some reason, when the MS one went off the market most were ball operated by the thumb and the buttons with fingers, whereas the MS one was t'other way round.