I've got low expectations for the third one given that the girl is supposedly going to be the killer - I don't think she's terribly convincing at all...
I'm with Rob on this one. The first one was excellent. The second one was good to a point. I picked up on the twist right away and did not find it all that believable. Too many clues to ruin the outcome.
SPOILERS below, beware
Another thing that bothered me on the 2nd one was Wahlberg being chained up in the original room that Cary Elwes character was in. Was this place so secluded that investigators never found the original bodies?
Unless the Killer is another person in the third film, it will fail with the current female character IMO. Also, although we see Jigsaw slumped over in the van, we dont know he is actually dead. It would be cheesy if he returned somehow.