Bests & Worsts Reviews from Amazon

I've been using the Logitech M570 exclusively for as long as I can remember. Currently I have 5 or 6 of the M570s lying around my house connected to various computers. I've convinced my wife, co-workers and a few friends to switch to the M570. The M570 had one major drawback--no bluetooth connectivity. Like a lot of M570 fans, I was elated to read a couple months ago that Logitech was releasing a bluetooth version of this popular trackball. And then I actually used one. For me, the Ergo is uncomfortable to use. It is the first time using a Logitech trackball for 20 years that I felt any discomfort in my hand or wrist. This will likely vary by individual, but there are four flaws to the device that have led me to abandon it: 1. The metal riser on the MX Ergo increases the height of the device which results in awkward hand/thumb placement as compared to the M570. 2. The extra weight and the textured grip nature of the MX Ergo means that it has less "give" when you move your hand onto it. Rather than my hand gliding over the plastic of the M570 (especially when I am reaching to move the cursor without looking at the mouse directly *or* if I'm readjusting my hand placement), the MX Ergo resists the movement of my hand. The result is something that I feel in my wrists after a few hours of use, and not in a good way. 3. The ball does not seem to roll as freely in the MX Ergo as it does in the M570. I used this for about a week before giving up on it. Four weeks later, I could still feel faint aching in my trapeziometacarpal joint. 4. As anyone who has owned an M570 knows, the ball needs to be removed periodically as dust, etc. will accumulate in the area that holds the ball. This is much more difficult to do in the MX Ergo. There is a hole underneath the ball, but it is not nearly big enough to fit a finger through. You'll need some sort of device small and strong enough to dislodge the ball, but also avoid scratching it. Really dumb design decision on Logitech's part. I have to wonder how much ergonomic testing of this they did, or if this is a quality control issue with these early units. It's a huge step backward from the M570 IMO.