Espruino as a way to mess around with a DIY quadcopter

I think it should be pretty easy to use Espruino for that kind of control system... It can handle sending and receiving the pulses for RC really easily, so you can just plug it into a normal remote control and use normal RC motor speed controllers...

We never heard back from @CamSwords but I think the only thing stopping his controller from working was that it was spending all of its time blocking, waiting for what he was printing to be sent down the serial link.

If you're interested in this kind of thing then making a Segway clone might be the best starting point. It's a similar idea, but with less chance of costly failures :)