Summary: I was really torn about getting this vs. the 608, but after reading about some issues with the 608's signal processing, I decided to save some dough and get the 508 (I really only need 2 HDMI inputs for my media room anyway). Boy am I glad I did. I used the microphone Audussy II tuning feature, and was completely tuned in 10 mins. I have a Panasonic ae4000 projector, and on a 11 foot screen, this is like IMAX at home (BETTER!).
Summary: I bought this to replace my Sony receiver I purchased from Amazon 3 years ago (almost to the day). While there was nothing "wrong" with my Sony receiver, I quickly realized once I plugged the Onkyo in, that my surround speakers were not being utilized as they should be. While I am not an audiophile, I do have some quality speakers, and I do like having a quaility sound while watching movies (and playing Xbox). The sound is so clear and crisp with this receiver.
Summary: Very rarely is there something I am willing to label as "perfect" when it comes to electronics. There is always something that can be improved/changed/modified to fit one's needs. However, I am willing to say that the Onkyo TX-SR508 is a "perfect" piece of electronic equipment. Quite simply, if you compare all of its features, ease of use, quality of sound, and its price, there is nothing better out there.
Summary: This reciever is so good I can hardly believe it. It is perfect for my surround sound system for my 55" Hdtv and 7.1 Onkyo speaker system. It is perfect for a relatively high end system for low end money. You would be crazy not to look at this receiver.
Summary: I got more than I bargained for. I had a 7 year old Sony, and the difference was amazing. I thought it was a good value at first. But the sound was so much better that I bought some Onkyo speakers. And those were so much better that I decided I would add a new entertainment room addition to the house. So $50,000 later I am going to be all set.