The main cause of choppy, slow or delayed video and audio is less than ideal network conditions. Not only is bandwidth a requirement, but the network must be free of interference and latency. Normal internet use on a network will rarely show any signs of high latency. However, latency will interfere with AirPlay applications like Reflector and AirParrot.
You may not notice choppy or less than ideal streams with standard AirPlay from iTunes or other applications. These applications are not real time and buffer content before transmission. As our applications use real-time mirroring, we're unable to buffer any content that's being played back.
Because AirPlay requires guaranteed transmission any dropped packets have to be resent, and lag will continue to build until the network clears or screen movement reduces bandwidth and it can catch up.
Latency can be caused by older network hardware like routers or wireless cards. Be sure the firmware on your router is completely up to date, and that you've installed the latest drivers for your hardware. Rebooting your router can also help.