Nice review! You saved me the trouble of adding much more as I find most of your observations close to my own.
I am coming from an Arcam AVR350 which tells me the more 'common' brands of AVRs have certainly stepped up. Not to say, Onkyo in general has not had good sound quality, as did my first one 13 years ago.
The jury is still out whether the 809 matches the Arcam in 2 channel performance, but at this point I would say it's very close.
Given that, I think there is a clarity I never got with the Arcam, that is present in the Onkyo. A little stronger upper bass as well. The clarity may be akin to the 'metallic' sound you refer to...it is quite subtle IMO, and I think room conditions have some effect on it. I can't say I notice any listening fatigue at this stage. But I appreciate greater intelligibility when watching TV.
I should mention I am running Dynamic EQ off and have yet to try it.
I like the operation of Audyssey. It seems to be a very competent process. It did set the crossover of my front mains to 40Hz. I set it up to 70Hz, my center at 60 and surrounds at 50. I think I like the balance better. It is more how I had it before, and my original setup was done by an ISF calibrator who sold me my previous system, using a sophisticated audio analyzer. He also miked it in several locations. Even at that, I think the Audyssey may have done some beneficial trims based on the previous recommendations for speaker placement.
This is not the best sounding home electronics I have ever heard, but it is very good. For a receiver, and for the price-point. My ears have aged quite a bit too, but then you would think I would be even more critical of sound in the higher regions. Unless nature endowed me with a very smooth cutoff curve.
I shared the nice surprise with video that you discovered. I get the same picture that if anything looks better than before. And I was running all my sources directly to my HDTV, not going through a receiver for switching. I have the inputs set at 'auto/direct'. I have a calibrated display and did not want to do additional processing.
My only disappointment is a small one. While I like the net tuning capability, I was hoping they would also include movie streaming (Netflix). As it stands it is just as easy for me to use my little Roku box and feed the HDMI output to the Onkyo for both movies and internet radio. But sometimes when I just want music I will still use the Onkyo alone. I am using a Harmony remote, so it is just a matter of pressing one button or the other.
I have a cheapie 7" monitor (Haier portable TV) next to my chair I use for viewing Pandora, etc. titles so I don't have to turn on my display or squint my eyes to see the readout on the Onkyo panel.