I've owned the 2014 edition of this mouse for almost 3 months now, and I find that the surface is starting to flake off under the right button. This is a fairly common defect with this mouse that I didn't know about when I bought it. The original packaging is long gone now so I can't return it which makes me pretty angry. I will definitely be contacting the manufacturer.
Other than the surface however, the mouse performs better than any mouse I've ever used - including my old Logitech MX518. It's light and comfortable to use. I have no complaints about the tracking and the mouse buttons just feel very natural compared to the MX518. It's a shame about the surface.
UPDATE: I submitted an RMA request with Zowie but they never responded to it. After emailing Amazon I was allowed to return the mouse even though it was outside the 45 day return period AND I did not have the original packaging which makes me a happy customer. According to Zowie the problem was with a preliminary batch, so I ordered another one from Amazon. However, I've been using that mouse for about 1.5 months now and the flaking problem has started again. I will be keeping the mouse this time but I will probably not buy another Zowie mouse in the future.