I think deathadder is the one of the few that doesn't function best at max dpi. I've read a bunch on OCN that 1800 is best on the 3.5 deathadders and from using the mouse for about 3 years.
I've got the Zowie eVo EC2 now and use it on the middle sensitivity, not the max setting, because I don't really feel a difference but at my level it probably doesn't matter.