I have been using the Deathadder for a month now. I will be comparing this mouse to my old one, wich came with the computer I bought (3 button regular mouse).
You need to know that I'm a gamer, and that I probably noticed details that most won't. My hand is average size.
At first, the Deathadder seemed to be a little big in hand since I was used with my small regular mouse. It takes just 2-3 hours before you forget about that. You won't notice how much of an ergonomic change this mouse is before you go back to your old one. I have 2 computers and right now I just hate using a regular mice, they really feel uncomfortable.
Both right and left click are smoother than a regular mouse, the middle click is tougher and the additionnal buttons are regular. Also the mouse physical configuration makes it so it is much easier to middle click with your index than it is with other fingers (so if you aren't used to click with that finger for middle click, it is another attunement you will have to go through#.
The rubber finish is nice, and so is the scrolling of the mouse. Once you download the drivers from razer website, you can customize it the way you want it # DPI, etc.#. I'm not sure, but I couldn't find any macro recorder in the Drivers software, as opposed to the Mamba #view mamba review on youtube to understand what I mean).
Aside from that, the Deathadder is a great mouse and I would reccomend it to anyone. It is much more comfortable than any regular mouse and you will quickly get attuned to it. 5 stars.