Pros: Sensor, comfort, build quality, well-braided cord
Cons: High lift-off distance, no on-board memory, bad driver, no sidegrip
I switched to the Deathadder more than a year ago. I switched from a very different mouse, the Steelseries Kinzu. I noticed that the sensor on my new deathadder was much better, but I also noticed a much higher lift off distance. This really annoyed me, as I play with low sensitivity (800 DPI x 1). I did, however, get used to it quite fast. If you play with a high sensitivity, it should be mentioned that this mouse performs well at high DPIs, too! And the lift off distance will affect you much less.
Anyone who has played an intense FPS for more than 40 minutes in one session (e.g a typical CS match) knows that comfort is really important. You don't want your hand hurting after just a single match! This is maybe the one thing I like about the Deathadder the most: Comfort. Unfortunately, the comfort is not perfect. If you play with the kind of sensitivity I do, you would probably agree that a lightweight mouse is important. The DeathAdder is NOT a lightweight mouse! It weighs slightly over 150g, which really is too much for me.
As I've mentioned, there are a few things that annoy me about both the sensor and the comfort of the mouse. There are a few more details that annoy me though. For instance, no on-board memory is really annoying. In addition, the bad driver just makes the mouse look like something a 14 y.o would buy to look cool.
I would like to conclude by saying that the DeathAdder 3.5G is a great mouse, and shines when it comes to sensor quality and comfort, but loses some points by lacking futures such as on-board memory, lower lift-off distance and the lack of a sidegrip. For me, at least, weight is also a detail Razer has missed at. If you agree with me on these points, you should look into the Razer Deathadder 2013, as it has resolved more than half the problems I have with this mouse. If you do, however, think that 150g is a good thing, and the lack of side-grips don't annoy you, I would definitively recommend this mouse.