content: I used the original until one day while cleaning it I lost one of the ball bearings. The original was awesome. Sure, it had to be cleaned from time to time but the ball spun easily, the cord was long, and most days it worked so flawlessly you just forgot about it. So since the original would catch without the ballbearing, I decided it was time to get the newer optical version.Ugh.My first one had dyslexia. Up would go down and vice-versa. Logitech was nice enough in sending a replacement but after a few months this one catches almost worse than my original without the ball bearing! Only the trackball doesn't come out so you can't manually clean it. Very frustrating and I'm currently looking for a new solution. If this trackball will be your daily driver don't expect the legendary reliability of the previous models. This one will only disappoint.