I have a Nanrobot D4 3.0 in the metalic blue and absolutely love it. I had a couple small issues and one of them caused a hairline crack in my front wheel hub.
After talking with Nanrobot they worked with me and got me a new hub in a week flat! They are always trying to help but also listen so they can better improve the overall experience of not only owning a Nanrobot, but repairing them as well...A+