Well, based on what I've listened to Dolby TrueHD tracks tend to be a bit low, you'll find yourself always cranking the volume up a little more to match what is generally considered "normal". They aren't usually "louder" like DTS tracks are.

It's also interesting to note most TrueHD tracks have been 16bit/48khz. Universal's HD DVDs all feature Dolby Plus at 24-bit/48khz/1.5 MB per second as their "standard."

Here's my HD DVD (& DVD) collection , if anyone cares. :p