Honestly, I've never found a mouse that was perfect.... (i.e. doesn't suck). There are mice that are good... but there is ALWAYS something missing or not working exactly right to make them perfect. You find one with good build quality, and then it doesn't have enough buttons in the right places. You find one with near perfect button placement, and the sensor or the software is all wonky... or they are either too light (or heavy if you prefer lighter) with no way to adjust (or if they do adjust they are missing one of the other requirements.
Sometimes I just wonder if some company would in fact try to build the "perfect" mouse that has the best sensor available, with customizable button layouts that would fit my hand perfectly, and have flawless software. (Yeah... I know this is too much to ask here... LOL).
Basically it would be like merging at Logitech (build quality) with a Cyborg (layout flexibility) and a Razor and only taking the best parts of each to make the ultimate mouse.
Ah to dream the ultimate dream.