Unreliable UDP for P2P gaming is a feature I'd like as well. For real-time games where you're managing 8, 16, or 32 players, you'd want to be able to send positional updates (that could be dropped, and would be re-synced the next time an update is received). In real-time games you cannot afford to wait for in-order delivery of the socket stream (because the nature of it you're actually managing 16+ parallel entity simulations, that are moving forward in time and lost past data can be resynced with current data.)
Researching it a little more it sounds like for Flash 10.1 RTMFP NetStream API has been modified to include configuration of NetStream.dataReliable.
source at 50:41 in the video: MAX 2009 - P2P on the Flash Platform with RTMFP
Partial Reliability Control at publishing peer
I'm not sure when Flash Player 10.1 beta will be out, but I'd really like to try it out and see how a real-time multiplayer game can work with unreliable UDP data.