Pros: Sound Quality, Ease of Use, True discrete output
Cons: Price, and that's about it.
After doing extensive reviews and trying the Onkyo 501 I bought the TX-SR601. Here's the system details: I have a small room with hardwood floors, wood beam ceilings and wood shutters. Tough room. I bought the Bose Acoustimass 10 III. Ok, Bose haters, I don't want to hear it. I bought them for specific reasons, size of room+size of speakers, and they sound great. They're a little difficult to get set up just right, but once done they're great. You can read my review of them under Bose. I have a Sony Progressive scan DVD player and the Onkyo TX-SR601.
The 601 has an on screen display so configuring the speakers, distance, sound, inputs etc was fairly easy. The remotes ok, easy to operate, but not spectacular. It is a learning remote and it was easy to program button to button from my TIVO remote etc. This worked out nicely. The only drawback is the buttons are not named well for this, but it works. Because of the Bose speakers and some help from a Circuit City employee who actually knew what she was talking about, I set the front speakers to large, center and rears to small.
Oh, and don't get excited about the Composite video switching, if you run anything with an s-video, like satellite, you still have to change the input on your TV first. Ok, so I played several DVD's including Two Towers, Patriot, Black Hawk Down etc. Here's what I found:
The sound is very natural and incredibly crisp. I immediately heard things I had never hear in my Sony 895. I also heard sounds I didn't hear in the Onkyo 501 and the Yamaha V730. The Two Towers had some specific things that I couldn't believe. I could clearly hear every grunt, sword and thump with crispness. The Bass is perfect. Not too boomy and it fades in and out appropriately with the scene, instead of booming around the room in a thumpy useless manner. I can't over state the clean, smooth sound this receiver produces. It's transitions around the room are great and the voices don't fade out leaving you overwhelmed with front speaker sound and missing the dialogue.
There were no tinty sounds, no bright sounds and the dialogue is very clean. There are a few sound field settings, but not too many. They produce small, but appropriate enhancements. They don't sound phony or reverbed like many other systems sound fields. Onkyo's sound is so clean, you won't want a bunch of sound fields messing it up.
Some important technical issues.. Go to Onkyo.com for the specifics, on DTS, Neo 6:1 etc, this thing has it all (except THX) of course. I'm just going to state a few important things. Compared to the 501, this system is worth the extra money. The 501 is an entry level receiver, made for the mass market who don't want to spend much on their receiver. It's a good, Onkyo receiver, but it doesn't compare to the 601. The 601 is truly discrete, it processes each channel and amplifies it separately, hence the clear crisp sound. It also has some of the asthetic features, such as a few more sound fields, on screen display, learning remote etc. If you're debating between the 2 don't, this one's it. Compared to the 601, the 501 sounded a little flat and empty at times.
Also if you're looking at Denon, Harman Kardon, and/or Yamaha, I can only say this. They're all great, discrete and high current. Denon and Kardon are not going to offer you as many features as the 601 for the same price. You're going to spend more for the same thing, but if you're die hard on those brands, save up. Yamaha is a waffler. It's a great receiver with a great set of features; on screen display, a million sound fields etc. But my feeling was the sound fields sound too "created" and unnatural compared to the Onkyo. I also don't like relative volume measured in negative deicbles.
If you're comparing the 601 to Sony's, JVC, Panasonic etc, you're shopping in two different worlds. You're comparing a Mercedes to a Ford Taurus. Similar size, but that's about it. Move up to Onkyo, or any of the above brands and don't look back.
All in all I highly recommend the Onkyo 601. It's got some great features, great sound, and the technical quality you expect from them.