I saw this recently as well. I was pretty thoroughly whelmed by it especially given that the makers of Saw and Paranormal Activity were behind it. I thought it was actually kinda funny in certain places. Like <spoiler>
Lol. Okay, that scene ruined the tone of the movie for me, personally, but that is rather cute/funny.
I didn't realize some Saw and Paranormal Activity folks were behind it.
I actually liked PA 1, and I just watched the entire Saw series back to back in the last week. I actually really like it, because there's a difference between John Kramer and his 'understudies' -- an actual method to his madness, a purpose that drives him, rules that he imposes on himself, and his goal is to somehow "rehabilitate" rather than destroy. So moral questions are raised: Is it moral to put people in a situation where they lose some things dear to them in order to save their own souls?
And of course the complexity not just of each trap, and each movie as it interlocks, but also of all the time-overlapping sequences and trying to get the chronology right in one's head of when events occur despite which movie they appear in, plus trying to figure out who is who... all that's pretty mentally stimulating.
The gore quotient is pretty high though.
Then again, Saw was vastly overrated.
Like I said, I think the cultural focus on it was stupid -- people seemed interested in the gore.
I was more interested in the moral questions and trying to figure out the multiple puzzles of plot and time in my head.
Enjoy Insidious. I recommend watching it alone, in a dark house, late at night, with the wind rattling your windows and creaking the floors.