Top positive review
Left-handed M570 + extras
Reviewed in the United States on April 25, 2016
Finally I've found what's essentially a left-handed Logitech M570. In fact, as long as the product holds up over extensive use, it's even better than then M570. It's got horizontal scroll buttons that can be remapped via the software, it's got a low/high DPI switch, a slow/fast mouse movement switch, and even an extra button on the far-left that activated with your ring finger. The ergonomics are a little off compared to the M570, but I'm sure I'll get used to them. The ball movement isn't as fluid as the M570's, but I'm sure that will improve as I wear it in. Also, contrary to the other review, the Mouse Assistant software is in English. And it's got most of the options you'd want.
EDIT: After using it for a few days, the ball was getting sort of stuck in certain places. I know from using my M570 that the ball will slow down as the bearings get dirtier, but in this case it was something else. A layer of crud actually formed right where the top of the ball meets the plastic shell, so I had to scrape that off and the ball was moving fluidly again.