I've played a few decent sized metal festivals here, like South By So What and Winter Jamboree (mind you, we are not a metalcore band - we play very periphery/deftones/machine head inspired metal with little to no screaming), and I personally don't have too large a polarized opinion about it. When we break into a faster song, I love playing off of the energy and movement as I like to interact with the audience. But, I don't particularly appreciate when guys just punch people for no reason in a clean section. So I guess I advocate for movement and interaction, not just mindless mma style stuff. If you wanna josh your friends around, sweet, but don't be that asshole who tries to kill someone appreciating the music.