I saw it, liked it. Though, I have to say I didn't like it as much as the first one. The first one was a lot more fun in my opinion. I love horror movies, and when you get used to them and immersed in them you get good at picking them apart. This one still has a good sense of fun, like the direct Last House on the Left reference. That was cute, a nice giggle. A couple things though.
Too many characters in this one. The first was cooler because it stuck with a horror movie axiom, a drama axiom actually, by concentrating on a very small number of people in an extreme situation. Kind of along the lines of Night of the Living Dead. With too many characters it's easy to lose connection and involvment with them.
The end was too easy to call, but that might just be me because I've spoiled my mind with this **** since before I can remember.
There really was no where to go with this as a series. Once the motive of the killer becomes obvious in the first one it just becomes an excuse for a franchise unless you can add something new. Kind of like the Hellraiser movies. The second one was a decent followup because it expanded the mythology of the original story. The ones after that were basically ****. With Saw, how many people can you honestly teach a lesson to before it gets boring?
Good things about it: more intense and graphic. A reasonably interesting situation for a group of people to be in. Some pretty brutal scenes. Good cinematogrophy, great look to the movie. Dina Meyers, who I've wanted to **** since Starship Troopers. Some hotties in extremis. Decent acting on the part of most of the cast.
Basically it held together and was definitely a better sequel than most. A good movie in it's own right. Worth seeing in the theater. I've got a little more faith in sequels now, the last one I saw was Ring II. That was a god awful piece of ****.