Lossless sound is pretty prefected. Dolby True HD is 96/24 or higher MLP wrapped in a Dolby Header. DTS Master Audio i beleive is PPCM with a DTS header and some Blu-Ray Disc just have straight LPCM which is basically raw audio.
Granted recievers that support the formats are a little rare right now, but all HD DVD players are mandated to support decoding Dolby True HD and out puting them over the 6 ch multi out. In short if you have a reciever with a multi-in (most do) you can have proper 6 channel Lossless audio. the only exception is the Xbox 360 which doesn't have 6 CH out.
Oh hey while we're bitching about the next gen of AV, did anyone catch that no current BD player including the PS3 meets the final ratified Blu-Ray spec? What's worse is they don't meet the Hardware requirements. it doesn't mean they're obsolete, but it does mean they won't support all the features of the final BD spec or all of the Blu-Ray java stuff. Thanks for rushing to market before the spec was finallized.