The last film I went and saw - Cars, it was not only the audience, but the cinema that spoilt the experience.
It was half term, and understandably, there were kiRAB in the auditorium. However, quite a lot of them, and I mean a lot of them kept on getting up and going to the loo, and what was worse was that I had the (pleasure!) of a door seat, so pretty much every 20 mins or so, there was one kid and parent going through the door. And there was this kid in front of us who went to the loo about 5 times during the film. There was also some crying kid too. The other thing that peed me off was the sound - there was no bass and the sound quality was pretty rubbish and tinny.
The other bad cinematic experience I can recall in recent times was when I found I sat in gum on my seat without realising it, until I got up to make myself comfortable - by that point the gum had been fused to my trouser leg/backside pretty much. I went and complained to the staff but they just stood there gawping, no apology, no offer to help get the gum off. I wrote a nice ranty/sarccy letter off to them but they never responded. Vue, you are named and shamed.