Just to be explicit, while this competes in the "tiny but breadboard-friendly microcontroller" market, it's not a nRF51 board (it's actually a more powerful chip, CPU-wise) and it does not have any sort of radio, bluetooth or otherwise.

The support from PJRC is great, though. And if you want to use the Arduino environment, I don't think anyone puts more work into making it work flawlessly on a non-AVR platform than Paul does, not even the Arduino guys themselves with their own ARM boards.