Axiom Home Page Forums General Discussion Technical Questions HD Audio Formats - Can you hear a difference?

I'm using a PS/3 at present to play BluRay disks (I've got a combo Bluray, HD-DVD for my HTPC comming) but got asked the other day if the HD audio formats sound any better (I use the PS/3 to decode to 5.1 PCM and push it out over HDMI to my Yami V2700).

Now I've not done any "double blind" type test and while normal DD / DTS and the new HD formats all sounds good to me (and leave me imersed in the movie) I thought I'd ask....
1) can you hear a difference and if so
2) given the law of diminishing returns, how much better is it

Thanks
Nathan