I went First Weekend.
I saw two guys getting arrested in the Do-Lab right next to me after they had sold some dude something. Three undercovers were on them like no other, poor guys weren't even resisting. I felt like taking off all my clothes and causing a distraction, but maybe that was the LSD.
I was asked atleast five or six times for coke, a few for molly and I was offered drugs tons of times! But I never sold anything just because I was paranoid. Undercovers are super easy to identify; they are wearing cargo shorts, loked, have backstage wristbands, and sunglasses and are scanning the crowd. Usually in pairs. The other kind of undercovers are higher up then they are in the Police chain, usually wearing khaki slacks and a button up bohemian t shirt. Usually they have ear-pieces and radios. And they are always over 20 years old at least.
Then there are normal cops, and you would have to be spun as all hell to not realize them.
There presence definitely killed some of the energy for me, but mainly it was just custy ass holes who think it's perfectly fine to push all the way to the front of a crowd only to squeeze right in between you and the person next to you.