Which version of the DeathAdder? I hear there's several, and the 3.5G/Black Edition version is the one to get, being the one that fixed the tracking issues and has a more solid build...or so they say.
All I know now is that the Mamba basically uses the same shape, and it's very comfortable. Since I don't need wireless functionality (and the DPI switch buttons blend in too much with the left mouse button to be practical, and I stay at 1800 DPI the majority of the time anyway), why not sell off the Mamba and buy the DeathAdder BE at a lower price, saving the extra cash for later?