I can't believe some of the negativity in this thread towards the G500, it saddens me!
In the past year I've used the G5, G7, Deathadder, Mamba, and G500 - I've used them for sessions of FPS (cod blackops/BF:BC2) and MMO gaming (wow) and had put a minimum of 1 weeks worth of use at 4-10hours of gaming a day on each.
I have to say that nothing comes close to the G500, the first thing that sold me was the inifinite scroll mousewheel. It was great for my warrior in wow. I put the most use into both the G5 and G500, so I guess I'm more biased. But I really did give the razer's a chance.
Also, on black friday, they were 35$ from newegg and I bought one for my sister and a friend. One was using a Razer, and the other a G7 - both couldn't be happier. The macro buttons are fantastic for wow, perfect placement, and the middle mouse isn't a hassle to click.
I kind of want to get a G700 now just for the hell of it because I like this one so much.