Some initial impressions.
The unit is DEEP! Much deeper than any of my previous kit. Which meant I spent the first four hours of ownership drilling holes in the back of my brand new TV unit. I am not particularly handy at DIY. However, it was marginally deeper than my unit BEFORE anything was plugged into it. If your unit is open backed not much of an issue but if you have one with a back it is something you might need to consider before purchase. Or buy a jigsaw.
I couldn't figure out how to use my lovely Chord Carnival cable with QED airloc plugs so went and got some new bare wire QED Silver Anniversary cables just so I could hook it up. Probably a step down in terms of quality, but I am not too concerned at the moment. I connected these to my Wharfedale Diamond 9.1's, so I am not using the speakers you get in the V501 package. Also, my setup has changed, so not only am I using different cable the 9.1's are no longer on my Nexus 6 stands but are sat either side of the TV on the bench top, so probably difficult to compare accurately.
First test - CD audio. Sounded a bit weedy and sibilant at low listening volumes. However it gained a LOT when turned up to even 'normal' volumes. Subsequently I realised that the system was set up to use a sub and the crossover frequency was set quite high. I have changed this now, but not tried the system with a music CD again.
Second test - Radio. Awesome. I have a dedicated FM aerial, which I don't think anyone else in the block uses, and the sound that came out of the speakers was truly great. So much that I may stop listening to digital broadcasts and move back to FM.
Third Test - Sound from TV. Connected to (analog) Video Input 1 and sounds fine to me. My prinicpal TV source is an IPTV box, which is fed into the TV via SCART (no audio outputs on box) and through the TV. Had to get this new amp because there was audio/video sync problems (60ms if anyone is interested) which is now corrected. So, stereo sound from the (probably compressed) audio stream was fine. Didn't really watch anything that would test this properly, so will update if I notice anything.
Fourth Test - DVD output. Video stream looked great outputting progressive via component. Disappointed that you can't output upscaled image via component. Not sure that I will bother getting the HDMI just yet - the scaler in my TV seems pretty good, so not sure whether the scaler in the Onkyo will be any better, and then whether undergoing another scale (720-->768) would degrade the benefit anyway. Also, can't be bothered to drill any more holes in my cabinet. I also altered the settings on my plasma, since I have been running in for a while, so can't directly compare, but the opening scenes of Fellowship of the Ring looked totally awesome, really 3D with great detail and colour. In terms of sound it seemed OK, although again haven't really had the opportunity to test this. Tried changing the sound from stereo to artificial 5.1 and it did put a bit more space in the soundstage. Will need to test this properly before I can comment.
So, at the moment I am pleased. I have converted a three box system into a one box system, for not too huge a cost and importantly I don't feel like I have lost a lot in sonic performance on CD audio, which was my major concern. I will update as I give it a proper workout over the next while.