Summary: However, the trackball I received came in a clear plastic bag I can only describe as coated in filth. Apparently this was a fairly heavily-used item previously, as it appeared to have food and skin particles which shook loose in shipping, resulting in a fairly offensive package. I understood that refurb. sometimes is a compromise, but I'm completely shocked at what I received.
Cons: I've purchased refurbished items many times in the past, and generally I've had no issues; a refurb. is usually within manufacturing specifications, and depending on the deal, may have a scratch here or there.
Pros: I had the corded version for a couple of years and LOVED it. I purchased that one after my Micorsoft one died, which was great as well.
Cons: As others have pointed out there is an issue with the left mouse button going nuts after a certain period of time. Mine seemed to go nutty after about 3 months. I noticed that if you click the left mouse button in certain areas of the button it will stabilize but that is not a solution. Checked the Logitech support forums and found I wasn't the only one having the issue. Unfortunately, Logitech's response has been little more than "oh, sorry. guess there's a problem. ...
Pros: Works OK for me others have some problems (clean your ball and contact points)
Cons: Ergonomics...Hag to use a grinder wheel to file down the top left small button, was annoying as hell. Used the corded version for 10 years + Next time use a designer who used a previous mouse for years, change is not better. I call this my Windows 8 trackball.
Summary: Stopped working after two months, can't say that I really liked it or got used to it either. I wrote customer service at Logitech: "To be clearer, the trackball by itself isn't carrying the command to the "reader" but if I remove the ball and move my finger inside (where the trackball goes) it does move the cursor but replacing the ball in nothing happens.
Pros: None the mouse stopped working after 2 months
Summary: Do you need your mouse to be accurate? Do you need to be able select text on the first attempt, and not on the twelfth? Does it make if a difference if you are selecting a file or opening it? If not then this mouse is for YOU! Mine is less than a year old, the LMB is shot. It works half the time, the other half it chooses to multi click, or not click at all. I've resorted to KB shortcuts to get around using this POS. Steer clear of this model, M570.