I recently added a Pioneer VSX-822-K to my setup (samsung 55", mac mini, comcast cable box- all going through HDMI/the receiver)
The HDMI options on my receiver include Control, ARC, and Standby Through.
I even notice a significant delay switching between hd channels, though i do notice that there is no delay when moving between channels outputting the same resolution. (for instance, channels in 60p experience no delay when switching.)
I could be barking up the wrong tree entirely, but it seems like the pioneer receiver is the only thing that has changed as of recent.
Thanks in advance!