If your looking for a mouse that would help you in MMOs, then you might want to try the Razer Naga.
Most of my buddies that play WoW and other MMOs use the Razer Naga. So figured I would throw that out there, and its fine for other games as well. But primarily its very useful if your main type of gaming is MMOs. With an MMO your not worried about having a perfect sensor. The ability to have more skills easily accessible is the number 1 thing with an MMO.
Also, Best Buy carries these, so really easy to try one out and return it.