I dunno, I think it depends on the bunny - mine are very forgiving about it if I have to flip them on their backside to clip nails or something, but I know some bunnies get stressed out by it. I don't do it very often and definitely wouldn't recommend it with a bunny who seemed stressed out by the experience. it may help that mine were 7-8 weeks old and already used to being handled when I got them, so they're pretty easy-going about that sort of thing.
I usually offer a tiny piece of fruit before and after to make it a more positive experience for them and once I've got them flipped back over so they're right-side up, I'll pet them from nose to tail until their teeth chatter with happiness - that alone is enough for mine to forgive the trancing.