I never thought this day would arrive. You can natively playback AVCHD using the new quicktime player included in Mountain Lion (avchd support is buried within the "200 new features" list on apple's site). Naturally, you still can't just play .MTS files directly, I mean why would Apple want to make it that easy..... but if you have the whole AVCHD directory structure, the "private" folder shows up as a quicktime playable file. Opening it will open a window that generates previews for all video files (this can take a while), which seems to happen every time you open package. The playback itself works very well, even on my old 2.66 Core2Duo Macbook Pro. CPU usage is much lower than when using VLC, and it does a better job de-interlacing, so I think it's FINALLY using GPU acceleration for the playback. Nice to know that I can (in the future) just hook a mac mini up to my TV, and play my camcorder files directly off the SD card without having to transcode anything!