Summary: I have had this mouse for over somewhere around 8 years. It has been moved between 4 different computers and 5 different houses. My kids have gotten the ball out and thrown it around/played with it and it still works VERY WELL. there is one very small scratch on the surface of the ball that slows it down on bit on occasion but it's more than outlived it's expectations.
Summary: I bought a used mouse which has a massively sticky ball, worse than my used-every-day-and-rebuilt-twice 8 year old Logitech Trackball. If you have to do anything with precision, this is NOT the mouse to buy. Consider buying an Anker 2000 or 5000 mouse instead.
Summary: I have used this exact mouse for about 10 years, give or take. It has never failed me and I have never had to get a replacement. All my buttons still work, lights functioning, connection is stable, etc. If you have the money, buy this mouse if you want a trackball. I've used other trackballs and I still keep coming back to this one.
Summary: I'm literally shocked to see soo many good reviews on this trackball. I've owned mine for various years and have never loved it. The major problem is that the ball sticks. Period end of sentence. Sure it works fine for about a few minutes, maybe an hour or so but somehow it is designed it sticks and I'm not the first to mention so although I'm the first to mention so here. Forward back buttons work good and scrolling is fine but the ball sticking is a deal killer for me.
Summary: Great little replacement for my Microsoft optical trackball. Works well I do wish the mouse was a bit larger. Very responsive and the transmiter fits in my Dell desktop and I can close the bay door. I would rater have a new Microsoft Optical Mouse but alas they quit making them a decade ago. Its the best trackball on the market.