I got the MX518, G5, G7, Razer Diamondback.

Mx518 = Perfect, could have more buttons on the side....
G5 = All the good points of mx518 but The weights are a gadget, scroll wheel is not low profile so it sucks if you used application like 3dsmax where you have to press scroll wheel (middle click) alot. I dont like the material used for the cord. The material on the mouse is too porous, like anti-slip material, i dont like that.
G7 = Same as G5 But wireless and loses its battery after 6-7 hours.. worst buy
Razer Diamondback = Really like the feeling of the mouse but, site buttons are really hard to get to and cannot be mapped for "next and back" in IE and Firefox, Middle button too hard to use.

I voted for MX518