I can't believe nobody's mentioned sound. That's what fucks up porn, from a behind the camera pov, for me. There's nothing worse than fucking around with the remote control, turning the sound up one minute then down the next because half the shit is a whisper and the other half is some chica screaming "FUCK MY MOTHERFUCKING ASSHOLE YOU SON OF A BITCH!" in the same scene.

Music really doesn't make any difference for me unless it's really, really bad.

One other thing, which I've only seen in "high-budget" porn: reusing footage. In porn, you're hanging on every frame, but some of these Vivid, Wicked, Adam and Eve movies actually use the same footage in the same scene over and over again. They're not disconnected from the sequence (usually) but its still a total buzzkill. Anything that reminds me that I'm watching a movie, whether it's Hollywood or porn, is bad, and shit like that does.