I have a similar set up, but using Feb 2011 MacBook Pro. Was experimenting last night. Streaming video via Internet to my lap top and then mirroring to the TV seemed to present problems. For example, streaming from PBS website and mirroring has video stop/start issues. However, streaming via the PBS iPhone app and mirroring to the Apple TV seemed to work fine, so it doesn't appear to be a bandwidth issue. Also watching streamed video on my computer was a lot smoother than streaming said content to computer and then sending it to the Apple TV. Need to try many more variations to pin point the problem and figure out if there is a fix. Maybe my computer needs to be closer to the wireless router? Would more ram help (currently have stock 4GB)? Is all the traffic on my wifi network a problem? I have yet to try mirroring downloaded and stored video - although this has worked perfectly via airplay within iTunes. Anyway, will probably learn more as experiment over time.