As of August 2012 all units are programmed with MultiWii V2.1. Some units purchased around that time may still be 2.0. Both 2.0 and 2.1 give excellent results, the altitiude hold seems to show some improvement in 2.1.

MultiWii 2.2 is now available and you can easily upgrade using the Firmware Config Tool on any Quadrino board.