Instruct: Classify an Amazon review into positive or negative sentiment.
Query: Best Trackball I've ever owned

I hesitated to spend $100+ on a trackball, but I've had no regrets since I've been using it. It is worth every cent.I don't use the 6 "quick buttons" on the top of it, nor the scroll button, since they are hard to reach, but the four basic buttons and the smooth and heavy roll of the trackball are indispensable.I especially like the tactile "click" that each of the four main buttons give when they are pressed. This is a minor point, but it makes using the trackball feel solid instead of mushy.I didn't like the blue plastic ball that came with it, so I dropped a billiard ball in and it is perfect. Very smooth, very heavy, very precise. (This is via USB on Mac OS X.)