Coming from the DeathAdder, the transition to this mouse has been smoother than any of my previous switches.  Although the electronics in it are completely different (it's laser instead of optical), it has a similar feel.  The default middle sensitivity is 1800, so that further aids the transition.  The chizeled sides make it easier to rack the mouse (pick it up, reposition), although it is very sensitive to sensor height: the mouse has to be completely flat on the mousepad for it to track correctly.  At first, I was pinching the mouse a little too firmly and that was causing it to track oddly.  Once you get used to it, though, it's nice to have the extra grip the cutouts provide.  It's definitely heavier than most mice... probably about the same as a G5 with 3-4 of the 4.5g weights... it's almost exactly the same as my modded DeathAdder, though a little more backheavy.  It's extremely sensitive... I've never gamed with a mouse over 2000 dpi, but even at the lower resolutions, the Mamba seems to pick up the tiniest movement.  I'm reserving judgment on the wireless performance until I can get the proper drivers installed but initially, I'm impressed.

All in all, I think it's the small touches that make this mouse... the dual-use (wired and wireless), the Techflex cord, the sculpted sides and rubber coating, the look and feel.  If nothing else, this is the coolest mouse I have ever seen.

On a side note, I may be getting another Mamba for free, since they had a problem with the mice coming off the pedestal in the packaging... I got an email with this in it right after I got the mouse hooked up: