To my own surprise MAVLink has grown way beyond my expectations, quite a few projects a
re now using it as their main protocol or have at least support for it. When I started to work on the initial protocol mid-2009 every encoding/decoding routine was hand-written, and we just needed something to report the detected patterns in the EMAV 2009 competition. It worked, our helicopter detected the patterns onboard and sent the correct name via MAVLink back to the basestation -1st place EMAV 2009 indoor autonomy competition.
The protocol evolved end of 2009/early 2010 when I rewrote it to be used as hard-realtime link for the flying machines area at ETH's Institute of Dynamic Systems and Control. By now quadrotors play piano with commands sent over an early version of MAVLink (I did not do the setup or the flight control algorithms, I just did the control unit to vehicle MAVLink communication)
MAVLink got in the meantime automatic protocol generation features. By now there is quite a list of projects using it, ranging from ground control stations to complete middleware solutions (including a MAVLink ROS interface). But before you sift through the list, make sure to sign up for the new mailing list if you're interested in further updates.
MAVLink mailing list and website
Autopilots using MAVLink
Software packages using MAVLink
Projects using MAVLink