So, quite a few changes have happened in Airtime 2.1.x and the biggest issue is that they are not yet properly documented. The wiki only covers the installation part and the manuals go up to 2.0.3
Here are some of the problems/features that I have seen while using airtime 2.1 that I have not found a workaround.
Most of the producers use windows and some of them use S.A.M. Broadcaster for their shows. In SAM (and many other broadcasting programs) there is no "username" in icecast connection settings, so source is the only one you can use. To overcome that problem, I 've set up the master source to have "source" as a username so that everyone can connect through master. That worked well till the 2.1.1 upgrade came. You see, in 2.1.1 it's considered a feature that the master button stays on even though noone is connected. Why would that be a feature? Why would silence in the broadcast signal be a plus? So now, when there is a show that's scheduled to end at 22.00 and the producer tries to switch off the master stream at 22.01, he CAN'T! Why? Because it's not his show. And even though there is no sound incoming in the master stream, airtime prefers to broadcast silence instead of the scheduled playlist.
I think that the whole approach in connecting to liquidsoap was brilliant, but was executed in a poor way. The inability to connect with popular broadcasting software (although not airtime's fault, it could have been avoided) and the wrong fallback implementation are really causing trouble, especially considering that it's been two minor updates and there is still no documentation released.

Just some thoughts I've had to help with the development of airtime, hope I wasn't too judgy on your great work!