-I haven't heard the DTS cinema discs on my system for ID4, but the LD seems awfully faithful, better than the AC3 Laserdisc. I've yet to hear it on Blu-ray, but if it was sourced from the DVDs mix, it won't be as good.
-The DTS trailer attached to JP and other early DTS titles was a slightly shortened version of the one we are used to seeing. We have the audio for it from the DTS discs of Jurassic Park, but no video exists anywhere. It would be possible with some clever editing to re-create it with the DTS trailer that appears on several DVDs. Basically, the only difference is that after THE DIGITAL EXPERIENCE blows up, the sound and image fade away into nothing after the explosion. It's a neat effect and was awesome to see in front of JP last summer at a 35mm screening I attended.