This is the second Trackbar I've had. i have been using one for about 6-7 years supplied by my company owing to some wrist pain occasionally developing from using a conventional mouse. the centre wheel has finally given up so I bought my own this time. It's great because almost no-one else in the office can use it!
The only irritation is the way it occasionally flicks across the screen or between screens if I try and hover too near the corners. otherwise I love it and it avoids any sign of RSI.