Screen Mirroring over AirPlay works great in general, but the video quality is a lot less reliable than when you're streaming a movie using Beamer (or iTunes for that matter). The video stutters every now and then. You may find this acceptable when watching a YouTube video, but it's very distracting when you're immersed in your favorite film or TV-series.
Beamer offers smooth playback and consistent quality, because it builds a buffer of video to prevent stuttering. Beamer also enables playback control (pause, fast-forward, etc.) using the Apple TV remote and you can still use your Mac for other tasks while the movie is playing.
Beamer supports all common file formats including AVI, MOV, MKV, MP4, WMV and FLV. Embedded subtitles and subtitle files are also supported; however, surround sound is not supported as of yet.
The application can be purchased at the link below for $16. A free trial with a 15 minute time limit is also available for download.
Read More [via RedmondPie]