I have the Sony BDP-S550 and wish I had a Panasonic. Didn't realize it until I got the Onkyo 605. The problem is that you can't force the Sony to output decoded DTS-HD Master Audio as LPCM 7.1, if your receiver is able to decode DTS-HD Master Audio. It uses the HDMI "handshake" to see if the receiver is capable, and if it is, it sends the bitstream DTS-HD Master Audio.
Why would this matter, you say? Because some receivers, mine included, cannot apply post-processing, like Audyssey EQ, when it is busy decoding DTS-HD Master Audio or Dolby True HD.
FWIW, you can force the Sony to output LPCM 7.1 for Dolby True HD sound tracks by changing the BD Audio Setting to "mix" instead of "direct". But when this setting is on "mix" for DTS-HD Master Audio soundtracks, the player downconverts it to regular DTS first, and then sends it as LPCM 5.1
This is a little known limitation of the Sony players. I don't know if the new players (360/560) are different, but I looked at the manuals and it seems that it is the same situation as my 550.
Get a Panasonic!
Mark