The creators really stepped their game up for this one.
There's a whole new depth to Jigsaw's, the villain's behind all of this, character. We see flashbacks, which explain a lot about his previous life as an every day person. And why did he become what he is now, in the movie.
When the detectives arrive at Jigsaw's lair, there's a whole new twist, as they find the monitors, and see the group of people trapped in the house. One of them turns out to be the detective's son.
Those eight people in the house are all very different, but they have something in common, which connects them all. It's very inciting to watch those people try to figure a way out of the nightmare they had awakened to.
The traps are as gory as ever and very nicely done.
The negotiation dialogues between the puppet master and the detective are.
There's also a perfect soundtrack. Charlie Clouser is really one of the best composers out there.
The ending had a flawless twist. One no one had ever expected.
In my opinion, without a doubt, the best movie of the series.