I had bought a Cherry DW 3000 several years ago for my desktop and it had proved to be comfortable to use the keyboard and the mouse was comfortable in my hand. I used both daily, and the batteries in both keyboard and mouse lasted a long time with a warning neon on each showing when the battery was running low. I was very happy with it. Then I clumsily knocked the mouse off the desk. I picked it up and the tracking movement was OK and left and right buttons worked OK. However the scroll wheel was erratic, because it went in a random up or down motion regardless of which direction I moved the wheel. It was only then that I realised how much I used it, and how frustrating it was that I could no longer scroll reliability. I had no hesitation in ordering another and that worked perfectly out of the box. I was left with my old keyboard which worked perfectly and I asked Cherry if I could buy another mouse to work off the same USB adaptor as the keyboard because if so I could still use my old set with my laptop. I was told that they were set up as a pair in the factory and it wasn't possible to replace just a part of a set. For that restriction I have knocked a star off the value for money because I had to replace both when only one was defective.