Microsoft Wireless Notebook Optical Mouse 3000

Pros: It works great for about a week

Cons: Terrible mouse. Unreliable after 3 weeks, almost guaranteed to break.

Summary: I've gone through three of these. The first one lasted quite well - worked a full 3 months or so. The second one would lag and would stop fully responding, which was annoying. Even after a battery change and tests on many different computers, it just wouldn't respond fully. It you tried to click, the click would go through once every 5 times, and moving the curser was just impossible as it would recieve only for a few seconds before not responding for a while again.
The third one - less luck. It worked well for about 3 weeks, then it just went down the drain like all the others.
I'd strongly suggest staying away from this mouse. Sure, it's comfortable, but unless you want to stock up on them, you'll find yourself mouse-shopping every few weeks.