I do not have a firm opinion of the 502 audio quality as we immediately put it to service in one of our theater systems before I could do any comparative testing. Its output was also going through the Audessey Pro Room EQ which I am not fond of (it is disabled now). Our main source for music was from a PC I had built which out of necessity, was connected via Toslink. I did not like that option much. So we paired it up with the Audiophilleo Async USB and that noticeably improved fidelity. So subjectively I would say it sounds very good if you drive it right.
On the HDMI front, I was concerned going in. But that worry was for not. The machine has proven itself very compatible, easily mating with whatever sources I have thrown at it from the PC which can be notoriously difficult to PS3. The adjustments on this machine are quite nice such as the multiple crossover filter settings.
Speaking of the PC, the front 1080p LCD is wonderful as we have both the PC and 502 rack mounted and I am able to view the output of the PC there for maintenance and such, eliminating the need for a separate monitory.
We have taken the machine apart and I have to say, this is one complex machine. Lot of PC boards with a ton of parts on them. It is in an entirely different class than any other AV product I have seen. The others look like empty boxes compared to this beast!
Misses so far are the very granular volume control which steps in 0.1 db values. Not a problem if you are using the knob but for automation control, where you are hitting up/down buttons, it can be very slow. There is supposed to be a way to get it to jump in larger units but we haven't figured out how. Been too busy to call them and find out if there is a solution.
The machine just oozes quality. You don't feel like you spent a ton of money and you got a hair more bits than the mass market products.
BTW, there is a special going on with B stock units that have been refurbished. It brings the cost down substantially. So much so that I have heard people buying them as DACs for their PCs! Given the built-in display, it makes for a nice unit in that application per above. So if you are interested, be sure to go and check this option out before the sell out the inventory.