I've had a CM Storm Xornet for a little over a year. Generally happy with this mouse, but yesterday the scroll wheel broke - it just scrolls with no resistance, and the scrolls aren't registered, either. I was curious so I decided to open it up. My apologies for bad photo quality, my camera is basically the cheapest thing ever.



Turns out the Xornet has a really, really bad scroll wheel design, at least to my inexperienced eye. In the photo above you can see a black round thingy - the rotary encoder, which registers the scrolling - to the right of where the scroll wheel would go in. It has a hexagonal hole in which a matching plastic end plugs in and then turns it as you turn the wheel. In other words, it's 100% mechanical and it all hinges on a thin piece of plastic. Predictably, it broke off.





That's a really crappy design, if you ask me. In contrast, the Logitech MX518 I had been using for 6+ years had a lot better one.



It has spokes like a bicycle wheel, and two things on each side which I assume are transmitter and receiver of some sort, and can detect optically when you turn the wheel. Then there's a stiff piece of metal wire providing resistance, or "steps" as you scroll. Now this thing can probably break, but it definitely won't break from mechanical stress, e.g. from scrolling too much!

TL;DR Logitech makes higher quality mice than CM.