I've watched a friend have a delightful conversation with his fridge. As far as I could tell they both enjoyed it equally. On the other hand, I have physically had to hold a chap down because he wanted to run out into the street and 'away', convinced that the SAS were about to burst through a window to kill him.
You pays your money and you takes your chance.
I once spent an evening dribbling happily with a sleeping bag over my head and watching the entertainment my mind chose to deliver in the pitch darkness.
Never had or been present for a bad trip. The first bloke I ever did acid with did hang himself six months later, though.