Would get 5 stars if the scroll functionality were a bit better. The trackball can scroll by twisting the ball clockwise or counterclockwise. The promo video shows this, a hand using four fingers to twist it. Doing this is pretty tiresome on the wrist. As noted, the scroller does make a pretty loud click noise, like a dial on a watch being rotated. I thought it was a new sound effect at first to then realize it was coming from the mouse. A person can get used to it pretty quickly. It didn't take long to learn to use the scroller functionality more effectively. After a day I naturally started using the pointer finger to hold the ball in place and used the middle and ring fingers to twist the trackball. A much more natural motion, after a *lot* of scrolling though you could still build up some hand/wrist fatigue. It's not terrible at, not at all, but could be improved a bit - drops the product one star on value. A minor comment, the rubber tab that is sticking off the left side purely for an extra branding label is annoying. The aesthetic would be a tiny bit cleaner if that were not there. If all you do is move the mouse around and click, you could use this mouse all day long with no hand/wrist fatigue. If you scroll a lot, take some breaks here and there. Otherwise every other feature of the mouse is perfect. The feel of the trackball is great in the hand. Smooth, buttons in great position, all are easily reached and don't suffer from accidental clicks. The wrist and hand position while neutrally holding the mouse is comfortable, and rolling the trackball around is quite effortless. I got this trackball partly to avoid the wrist strain of moving a mouse around a bunch. For the most part it helps a lot, but doesn't go quite as far as I would have hoped given the scroll functionality. Overall, excellent product.