I see nothing about dynamic compression in there, really, it seems like raising/lowering the volume per-song... Not really Voladj-like, but more of a fixed +/- factor per song.. or am I reading that wrong?

Unless the tag somehow contains moment-to-moment volume data for the song (instead of a single field representing a single relative volume number), then your assesment is correct. It's a single volume adjustment, not dynamic compression.

However, some would argue that this is better than dynamic compression.

The two things solve two different (but similar) problems. I'd like to see both implemented, and choose between the two.

My only problem with doing relative volume adjustment on the empeg is that if a song gets played at much more than +5db beyond where I've set the volume control, I'll start to clip it because of where my amp gains are set. Dunno how the relative volume offset handles that, does it always attenuate or sometimes boost?