Alright, here's the gory details...
-Descent runs fine with or without VDMS, but insanely fast - if my memories are correct, something like 2-3x the speed it should run. (Running it without VDMS results in no sound, but it's still fast; so I don't think this is a VDMS issue)
-Using Speedset causes Descent to exit back to the desktop with no messages as soon as it starts. It actually worked once (and then stopped working again, despite the fact that I changed nothing; a race condition, perhaps?); however, this resulted in noticeable slowdown in high-poly areas...and speedup in low-poly ones
-The mouse and keyboard ship-rotation controls are incredibly sluggish, and seem even more so due to the fact that everything moves so fast.
-D1X has a framerate limit option, which from what I've heard ameliorates the control issues as well, but D1X doesn't work; running it with VDMS results in it reporting that it couldn't initialize sound or video, while running it without causes it to report that it can't detect the soundcard and then (unlike stock Descent) exiting.
I'm going to try getting it working on the pure-DOS rig shortly, but that's going to take some driver installs and it would be nice to have it running on my main system.

Specs:
P4P800 ASUS mobo
P4/2.6GHz CPU
2x256MB RAM
Win2k SP4 (for the purposes of getting this working)
Radeon 9200 video
Audigy 2 sound
VDMS-2.1.0-beta