Dolby True HD vs. DTS HD

Very slight, if any difference. I have heard that DTS uses less compression than Dolby, so that is the reason for marginally better sound.

However, I still cannot hear the difference between regular bitstream and the new lossless codecs.

If you can't hear the difference between bitstream and lossless Longhorn you probably aren't playing the recordings back correctly. There is a major difference in quality.

Rwwear is right, we heard a major difference! Night and day...

To me, DTS-HD is a little more dynamic than Dolby True HD. But overall very close.
As stated above, Night & Day difference between the older bitstream DD & DTS and the newer lossless formats. Sound was a big factor to me when going to Blu-ray.

I vote with Rwwear.