Note: there is an update to PP (5.5.1) that apparently fixes some AVCHD playback issues on Macs. so I may come back with good new (or not).
Well, that helps somewhat with playback of AVCHD (even edited) footage, but this is still too jerky at 1/4 resolution on my system to be called "playback". I think I will stick to transcoding first, then replacing the footage with the original AVCHD just before export.
