I have tested a flight controller called Falcon F4 for some time and it has worked great. Up until now it has been mostly bench-testing while developing firmware and GCS in LibrePilot. I will use it in some flight testing as well now when the weather here in Sweden starts to get more humane and predictable
The hardware is compatible with OpenPilot Nano board but got the same form-factor as the normal sized boards.
Its not as cheap to buy as the Nano but it seems to be high quality.
Heres a link to the board:
[size=78%]http://www.farwestrotors.com/[/size]/Fredrik