From the titles I have seen so far in both the Blu-ray and HD-DVD camp (MI:3, Superman Returns, and 300) the video seems the same, but the interactive menus look slightly better on the HD-DVD side. But, the audio slightly seems a bit clearer on the Blu-ray side. This is not an endorsement of any kind, just an observation.
On a side note: I think lossless audio or the lack thereof won't be a determining factor in the DVD Wars. That's not to say it shouldn't be included in the titles themselves.