I've also noticed that HDMI audio quality with the 5700 is good. Having tried HDMI with various receivers (Yamaha, Pioneer, Onkyo) in the past, I can say that it's much better with this. I can't use H.A.T.S. without a compatible player like the 5400ES but I know someone who has it and says that I won't really need it since I'm using a high quality HDMI cable anyways. No THX on this but the DCS modes are nice.
Any opinions on the Sound Optimizer? I've used hifi gear for my music years ago and I think that when it's on the Sony sounds like a good integrated amplifier with the tone controls set at 0. At first I was getting a little too much bass but after moving the speakers away from the wall a bit it's pretty much neutral sounding now. At least I won't be wondering where my bass is anymore.