The few people I know who've gone vegan due various reasons and motivations (a surprising number being BF mums who found baby had issues with dairy) say they feel amazing.
AIBU to think it's due to concentrating more on healthy eating generally? And potentially as milk can inhibit absorption of some things e.g. Iron. And maybe it's just the milk or the meat?
I guess I'm hoping for a relapsed vegan may comment!