For one the first movie wasn't very good (so your expectations are low anyway). BUT this movie is WAY worse. The dialogue is terrible and at times the acting is almost laughable. Nick Stahl has been in some decent movies, but in this he looks like he's just come out of rehab and took this part for a quick buck. He clearly didn't read the script or watch the first movie, which makes me think he didn't care as long as he got the work.
If your watching it for the shocks, you won't find any in this which actually "work" (not unless your of an extremely sensitive disposition at least). A character doing "insane things" in a mirror while a "normal" person at the other side of it "isn't" can only work SO MANY TIMES (like once) before your completely bored and used to the whole thing.
No story. No plot. No believable characters. No dialogue. No scares. No decent effects. No decent nudity (at least get REAL looking women, not plastic surgeon modelling wanna be actress rejects). Not worth renting.
At the end of this movie one of the characters screams. I knew EXACTLY how he felt. I imagined he'd just watched the movie himself and was sharing my pain.