I recently upgraded from an Onkyo HT530 receiver to the TX-NR509 for its HDMI and some of the fancy extras (networking, USB playback, etc.)
Some thoughts on the receiver:
HDMI issues from last gen of Onkyo receivers?
Doing a little research before buying, I was worried that the HDMI handshake issues that popped up for the TX-SR508 and TX-SR608 owners would be present here, but so far so good. Currently using it with a PS3, no issues so far. Will definitely update this if I come across issues.
The old receiver didn't have the Audyssey EQ configuration, using it was interesting. The set up process ended up pretty darn accurate in terms of automatically configuring speaker distance and values I'd normally have to put in by hand on my old receiver. +1 for painless initial setup!
Great On-screen display
The OSD is actually pretty clean and makes the menus easy to navigate. I'm not used to being able to configure so much without staring at the receiver's built-in display (which is actually pretty cool to look at). The OSD for network-based playback is a bit simple, but it gets the job done.
Mediocre Network-capabilities (Fixed via new firmware!! See update below)
A large part of spending a little more for this model over others I was considering was the networking capabilities. It was very cool to have it connect online and download a firmware update. Hopefully this means there will be an improvement on the next part: the DLNA playback for the receiver. This is where I have the most trouble.
I have PS3 Media Server set up on my home server and it diligently serves media to the PS3 via the gigabit network without problems. The TX-NR509 is able to see it and connect to it, but that's when the problems start. I haven't pinpointed the cause of it yet, but from what I've noticed, folders that contain "lots" of sub-folders or files (I'm just talking about over 20-30 here) cause the receiver to error out and force you to go up a directory/level and try again. Some directories only containing 1 file refused to open (I couldn't figure this one out). Letting it sit there and populate the contents of the folders didn't help either.
I was hoping I could play music off the server without turning on the PS3 and television, so the DLNA problems I'm experiencing are a little discouraging. Luckily, it's possible that Onkyo can remedy this through a future firmware update.
From Rodney's review, I tried the free Android app OnkyTroller on my phone to control the receiver. It does the job, but the app looks pretty ugly and seems somewhat limited in terms of functionality. Still, very cool idea. I noticed simply browsing through DLNA directories using my phone caused skips in music when playing from the network (too much network activity for the receiver to handle?).
-The TX-NR509 only gets warm after hours of use (way cooler than my old HT530)
-I love the 'Dynamic Volume' function of the receiver, it prevents opening theme songs of TV shows from blasting and helps us hear softer dialogue without fiddling with the remote
-This receiver is pretty tall compared to the one it replaced, plan accordingly if space is limited
Update: January 2012
Onkyo has been pushing out several firmware updates since my review in May 2011. The small bugs in the DLNA network playback capabilities have been ironed out and I'm able to navigate through all directories on the server with no issue. That was my biggest issue with the receiver that made me give it 4/5 stars, so I've updated my rating as well.
Lastly, I highly recommend grabbing the free, official Onkyo Remote app for Android. Not only can you push music from your device to the receiver, you can use it as a remote to visually navigate through your network or Pandora/music stations without turning on your TV. The official app is available for Apple devices as well, but it's slightly different/stripped down, making the Android version the more robust of the two.