The RAT mice are really nice to use, I have a RAT 3 for CAD and gaming and even though the back and forward buttons are on the same side (crap for leaning in games though I dont play very often anymore) its finally eclipsed the 5 button Microsoft Intellimouse in my own view of comfort and useability. Its also nice and easy to set up and use the different configurations and DPI settings you can have at the touch of a button. Only problem with it is that EVERY person who sees it for the first time has to ask A: what is it? B: why do you need such a fancy mouse? and C: Go on then, how much did that take you for then? It only cost £25 at PC world btw.....
I tried one of the Razer gaming mice once and couldnt turn the sensitivity low enough to use it, let alone get comfy with using it on their own mouse mat (expensive hard ali tat IMO). I would quite like one of the fancy RAT 9's but I dont think it would be a major improvement and still has the back/forward buttons on the same side.