If you liked the first 2, this one might be worth renting...maybe. It was a big drop off from the others.
I liked "Saw". "Saw 2" was waaaay too by-the-numbers...more of the same with the inevitable plot twist. I was hoping Saw 3 would rebound. But it got worse. It just never really hit a plateau. I think the story concept was actually better than 2, but execution was pretty sloppy.
I liked the soundtrack.