Microsoft SideWinder X8 Mouse

Pros: Comfortable fit.

Cons: Interferes with WiFi signal, wrecking it's usability.
Blue light is actually worse than (previous) red lights.

Summary: The mouse shares the same wireless frequency as Wifi, regardless of whether it's plugged in or not. So if you use a wireless internet connection, expect poor performance from both your mouse *and* your internet connection. The mouse will be jerky under heavy internet load and/or your internet connection will slow to a crawl.
Furthermore, the blue light that is heavily promoted for this product (which is supposed to work "even on wood!")(which it doesn't by the way) is actually worse than the older red lights used on previous mice (which worked perfectly well on wood).
Do yourself a favour - avoid this poorly conceived (but nicely packaged) product. It just doesn't work.