So far, enjoying A3. I did find a bug though (and confirmed others are having this issue - on Apple’s Aperture discussion forums).
Currently, Slideshows exported for Apple TV (720P) will not transfer/Sync to the Apple TV. The “theory” from the discussion forum is that A3’s export is saving at 30 FPS, while Apple TV is limited to 24 FPS at 720P resolution.
I have not discovered a work around yet for viewing slideshowns on the Apple TV.