Nice find! I just tried it, and thought it sounded much bigger off the bat, then I realized that it was mainly because the output volume is louder when it's on. I have to keep adjusting it in order to keep output levels the same.
yes, you're right but isn't it that way with tons of usual plugins aswell? Even when you match the volume you'll notice a nice enhancement with VM Tube. Nice warmth, richness and sparkle is what I hear and to be honest I wasn't dissapointed once (I tried on many sources).