I have not had any issues with the device; and, it sounds great with the speakers and sub-woofer I have connected to it. I live in an apartment so I don't get to use it to it's full potential often, but there have been a few times I cranked it up to see what it can really do, and it did not disappointed. Sure a large factor when it comes to the quality of sound has to do with the speakers that are attached, but music and movies come in crisp.
All of my devices (except for Ethernet) are attached via HDMI. The HDMI pass-through works great with no loss in quality, even when the device is turned off. Having the ability to attached all of the devices to the reliever and then only have one HDMI running up to the TV makes it much easier to have a clean-looking cable setup running out of the TV.
**NOTEs** 1) I'm not a fan of 3D at home, so I cannot tell you how well the HDMI pass-through would handle the increased data requirements of 3D.
2) I live in an apartment which is not set up well when it comes to using the 2nd zone option on the receiver, so I cannot speak to how well that function works.
I'm disappointed by how often audio and video loses sync on the device - far too often. It will happen while we are playing back something recorded on a DVR, something we are watching live, or less often with DVD/BluRay. It doesn't last more than a second or two, but when it happens 3-4 times per hour - well, I'm really to replace mine. Cable box / DVR is Comcast RNG200 with Comcast, DVD/BluRay is playing back over PS3 (rated the "best" BluRay at the time which is why I bought it - never played a game on it).
I only use it as an audio receiver, so I cannot comment on the video channel. I have three B&W M-1 satellites (configured as left, right and center) and a Velodyne MicroVee 6.5 subwoofer. I paid much more for the speakers than I did for the receiver, and I can say that they make a huge difference in the quality of the sound I get. My Onkyo TX-NR509 does not get in the way of the speakers. :-)
Regarding the Onkyo, if you go through the Audyssey EQ setup, the complete process, not the quickie process, the results are well worth the effort. I'm very happy with the quality of the sound. It is very easy to tell a good recording from a bad recording, and the good recordings sound great!
I generally use the unit in 3.1 PL-II mode, playing back 320k CBR MP3s that I have ripped from my CD collection (along with a few 320k bps and 256k bps MP3s purchased from Google and Amazon). Frankly, I don't think more receiver is going to make standard CDs and MP3s sound any better. You'd have to be listening to full 24-bit 96kHz uncompressed or higher streams, through some very expensive speakers, to hear any difference.
My advice is put the money into the speakers, this receiver is up to the task, unless you are into high-end audiophile equipment.
p.s. When configuring the Audyssey EQ profile, do not just place the EQ mic on the back of your couch or similar furniture, the sound will be distorted and muffled by the fabric and will not give you the best results. Perform the calibration with the mic mounted on a tripod or monopod, about 5 feet in the air, to get your best results -- and make sure the room is totally quite, no refrigerator or fans running, no open windows, etc.
Its an excellent receiver, and has performed perfectly for me for over a year. Setup was easy with the included microphone for sound field adjustment, and it makes my speakers and subwoofer sound better than ever. The internet radio puts the music of the planet at your figertips, PLUS if it is networked, it can find and play music from your computer/laptop, and make it sound excellent! And it comes on automatically when I turn the tv on. 5 stars! Sound quality is excellent!
I tried to attach my new Sony BD player to the stereo, and it could not handle the signal. It also does not like my HDMI feed from my $60.00 HDMI card in my PC. However, I feed all my audio from my various devices through it, and they all sound extremely clear. My cable box HDMI works fine through it. I am able to feed all audio back to my PC for audio recording with no problems. It handles my 15+ year old tape and record player inputs very well as well.
I have the player connected to Oppo 83 & Cabletv HDDVR box via HDMI and they both work great with the receiver. blu-ray movies, 1080p & lossless audio look and sound great. all of the cable tv shows look great too. i haven't had a problem with the receiver yet. before i set it up to stream my music over the network, i would connect my iPhone 4 to the receiver via it's USB port and it sounded great. the receiver has plenty of power for my speakers and my room size (15 x 22). i run a 5.1 system in this room and the receiver does a great job. it sounds great during football that's broadcast in 5.1 as well as blu-ray concerts. i can control it completely via my iPhone or iPad with a couple different apps. i can turn it on or off from anywhere in the house. i know you say you don't care about networking but it's a very big part of this device and a hugh part of music lovers. it streams music very well from internet radio to music sites as well as from your pc; that's all i'm gonna say about that. despite the fact that this model is being phased out for the newer models (and they are nice too) if you find a 509 it's still a nice value. unless (dare i say it) you want more advanced networking abilities then you want to go with a newer model like the 515 or higher. best of luck to you whatever receiver you decide to purchase.