I went from a Logitech G5 to a Coolermaster Sentinel storm and have not been sorry yet.I have been using this mouse for 3 months and its the best one I have ever used.I use it with a Razor destructor mat and its absolutely brilliant.
If you can, get your hands (literally) on an array of mice and get a feel for them, different mice suit different hand sizes / finger lengths / click pressure / movement distances etc etc.
That being said, I have had an Logitech MX518 for about 4 years now and if it broke, I'd buy the exact same mouse. It just fits perfectly in my hand and it is awesome if you don't want to take out a loan for a mouse and have 325 buttons to press with 5 fingers
I have the Coolermaster Storm, I got mine from take2 and i love everything about it!
the custom profiles allow you to change everything on the mouse and it stores 5 custom profiles.