OS X 10.8 AirPlay support
In OS X 10.8 AirPlay mirroring (both audio and video) is built in across the system. This means that you're finally able to mirror audio and video without having to use utilities such as AirFoil.
In Quicktime on OS X 10.8, when AirPlay mirroring is enabled, the video is in sync with the audio from the AirPlay-speakers. There is a short delay when mirroring, which Quicktime then can sync up.
When trying the same thing with VLC the audio is a few seconds behind the video because of this delay.
If possible, VLC should sync up the video and audio when using AirPlay mirroring.