There is no proper end-all ergonomic shape, the best you can do to combat RSI, at least from what I've gathered so far, is variation. I would suggest maybe getting two mice of very different shapes, or possibly something like a trackball or rollermouse in addition to a normal mouse. Personally I regularly switch mice, I also have a trackball on the left side of the keyboard. I like to believe that the variation reduces the risk of RSI, makes it easier to justify buying more stuff >_>
Though I would have to second the Abyssus for a no BS mouse, I have one that I removed the LED in, it was a fairly easy and painless task. Separating the two outer shells can be a pain, though, but you can still disable the LED without physically removing it.