I am very happy with the apple TV port of PMP, its so much easier than on my Mac. One function I really miss is the audio delay - my TV has a delay in the video chain, and the aTV audio output going to my amp is in advance. I normally delay audio in the mac mini client, but aTV client does not seem to have this ability. Till its available I'm forced to watch movies with my TV's speakers (which automatically adjust).
Another thing would be nice is the verbose OSD the mac app has..its great for analysing problems