Depends on how you have things hooked up. Lossless audio formats (multichannel PCM, TrueHD, or DTS-HD Master Audio) can be a great experience under the right circumstances, although like anything else they rely on the quality of the master source. (Don't expect to hear a huge difference between DD and TrueHD for a title that is predominantly dialog, for example.) You need to be able to get to those new formats, though. If you can play those formats and you have a surround setup, the new audio options are a definite plus for Blu-ray over DVD.

If you are talking about HD-DVD vs. Blu-ray, the two formats should be directly comparable (equal) in most ways. That's one reason the format war was so foolish to begin with. HD-DVD has less disc space, so you may see cases where more compression was used and a Blu-ray release may have an edge on video, but that's hardly a valid across-the-board guarantee. In fact, some early Blu-ray releases relied on older compression algorithms and couldn't match HD-DVD even with the extra disc space, although studios have by and large gotten past that phase. The HD-A3 lacked multichannel analog outputs, so the only way to get TrueHD (the only lossless format to see much use on HD-DVD and the only one supported by the HD-A3) was via multichannel PCM over HDMI. Otherwise, the best you get is Dolby Digital over optical (or DTS for HD-A2 owners like myself) that's encoded on-the-fly from the decoded TrueHD track. A player like the BDP-83 or the Panasonic BD55 will/can output decoded TrueHD and DTS-HD MA (which is showing up pretty regularly on Blu-ray these days) over analog for folks who lack HDMI v1.1+ receivers and processors, which is going to be a better route than DD from the A3.