My last mouse became so unreliable that I couldn't use it even for typing. When the button was held down, the switch was registering very fast click-and-release, so I couldn't highlight text or click and drag or anything! I do a lot of reading at my computer too, so it doesn't help when the scroll wheel isn't up to scratch.

I am fully aware that $100 is a silly amount of money to spend on a mouse, but I have few vices and a nice mouse makes a real difference to me.