The processing could not be much better, but the materials used. As described by others Rezessenten, starts after some time the plastic due to the salty perspiration hand to disband or to be rough. In particular, the palm and the convex inner hand below the index and middle finger. This is a shame, but I have observed with many mice. However, the relief of tendon weigh this drawback mE to clear.
By sweating per se, I also had the hot summer (south-facing windows) no problems other than the aforementioned stronger material wear (with other "normal" mice I have not experienced so quickly).
The keys are well-made, total one must be constantly a kind of remove "dirt", as tends to occur on Mouse - only too happy to bare right buttons. The biological residues seem to be (similar to the sticking of the good old mouse ball after some time stuff). That's a pity, but can probably avoid poorly and is not attributable to the product in my opinion.
On the additional keys you get used to very quickly, also to the third mouse button and the forward and backward functions. "Before" very unconventional, but as an explicit middle button is also available to fit over a pressure on the scroll wheel. The bottom thumb button I still did not use before. The cruise control buttons are directly below the middle finger approach, however, I have never come in the way.
In weight, the Evoluent lies comfortably in the hand. You get used to not forget to raise your hand higher than with a traditional mouse when you want to go back to the keyboard - initially you will be "stuck" because often times. The "stay tuned" in the Umgewöhnungs phase beginning worthwhile.
I am approached regularly by colleagues on this "strange" mouse and then reports always enthusiastic about the ergonomic function (the more natural hand position) and the fact that I no longer want to go back and it's a great relief - on the site there is relatively little invest quite a lot of money for his health. In particular, in an office job.
Mainly because of the ergonomics, I would buy it again. Evt sometimes because my office table's already become very crowded in a wireless variant ;-)
But I would prefer a little more processed from quality materials variant - hopefully there again sometime a successor. The market for Vertical Mouse is still badly served ...