Logitech MX ERGO is the updated version of the M570 - now with a tiltable base that allows you to adjust the angle at 0 and 20 degrees for extra comfort, precision mode, and Logitech Flow. If you suffer from wrist pain, this trackball might be just what you need.
After years of using a MacBook Pro, I felt the need to have a multiple monitor setup with everything that it implies - namely an external keyboard and mouse. I tried an old travel Logitech mouse that was laying around, which quickly started causing wrist pain. After returning 4 different mice for the same reasons, I found that Logitech had just released what looked like a better M570 - the legendary trackball I heard so much about in the past. Bought it, tried it, and the pain went away after a couple of days. If you're suffering from RSI, you should definitely give it a try.
Pros:- Great for those who suffer from RSI
- Adjusting to the trackball was rather quick
- Precision mode is great when working with graphics
Cons:- Might be too big for smaller hands
- Doesn't have the MX Master scroll wheel