When you are looking for a good mouse, you always find lists of 'top mouses for gamers'. However good mouse is also very important for developers. People who spend most of their time on computer. Usually we use various of applications and moving between them is like playing Call of Duty. When you want to click maximize button in VirtualBox or VMWare and you hit close instead, you are dead (VM start closing). You need to start your mission over (run the VM again). Some developers have problems with their hands (pain) caused by mouse use. It is good to invest some money in mouse instead of buying the cheapest or random one. However I have never spend on mouse more than $30. I tried various types of cheapest ones and medium-price.
Five years ago I made one of my best purchase: A4-Tech XL-750BF. I paid about $20. It was very good mouse in the notion of precision and comfort. I like to have high DPI. This mouse has 6 modes: 600-800-1200-1600-2000-2500 DPI (adjustable by a little key on top). I use to work on 2500 DPI. Unfortunately, after 3 years the left key broke down. Not completely though, but when I was dragging items, sometimes they were dropped when key was still pushed (instead of MOUSE_DOWN I had MOUSE_DOWN-MOUSE_UP-MOUSE_DOWN sequence).
Then I decided to invest in better brand and I bought Razer Salmosa. I found good deal on eBay for ~$25. It was quite good, but too small for my hand, and not that comfortable as A4-Tech was. This mouse was good for less than 2 years. Then (again!) left button broke down. Maybe I am not using it appropriate?
After that I thought my next mouse's left button will probably be broken too after some time and I decided to buy the cheapest Logitech: M100 ($7 on eBay). It is good mouse, but only if you do not have any other. A few weeks after purchase I found new A4-Tech: X-748K. It had good reviews and I decided to buy it. And again A4-Tech becomes very good choice. I paid $20 and I love this mouse! It has also 6 DPI modes (like X-750BF): 600-800-1200-1600-2400-3200. It fits perfectly to my hand and is nice in touch. The slightly rough surface is very cool. I am using it almost three weeks and it's working fine. It is the best mouse I have ever use. We'll see how long it lasts :)