I've seen this movie twice... the first time I was somewhat disappointed with it, as like some of the other reviewers, I thought there wasn't enough gore, tension, and scary moments.
Strangely enough, I really had fun watching it a second time, and here's why: instead of watching it as a horror / slasher flick, I watched it as more of a murder mystery... who is the killer? What is his / her / their motivation? In my opinion, the best moments of this movie are when various characters run through their various hypotheses regarding the killer and motive. The screenplay was well-crafted, so at any time the killer may be any one of a number of characters. Some of the dialog between characters is quite amusing.
So if you look at the cover, and think
hockey mask + chainsaw = gore, gore, gore
you'll undoubtedly be disappointed. But if you keep an open mind and play along trying to figure out the killer and motive, you should enjoy the flick. The soundtrack to the movie is excellent, considering that this movie had to be super low budget. The actors also do a nice job.