I have one, and have found it quite excellent. Easy to play around with, pretty good documentation, and the eink is really nice. There's something like 30 watch faces already designed, so you can just fork off one you like.

Highly recommend the anodized aluminum case. The plastic one is sturdy enough, but with the thickness of the material, makes the watch feel bulky. Also, the aluminum one has such a good fit (they are precision CNCed) that it can handle water splashes with no problem, and a few gaskets can get it to IP64 or 65