Pet peeves:

Excessive overdubbing on the soundtrack. Especially when the "sounds" have absolutely nothing to do with what is actually going on. If you're going to add moaning and groaning later, at least make it possible - if the chick has something stuffed halfway down her throat, she's not going to be begging for more at that particular moment.

Apathy. Too many actors mailing it in, some of the directors just don't care and the video companies will release it anyway.

Boring scenes. See "apathy".

I agree with whoever it was above who said male actors who don't shut the [censored] up.