I missed this at my local theaters and had to drive half an hour to catch it at a second run house. It did well at the box office, but I didn't like it much. As some of my readers will know, I'm a ghost story fanatic but what I like is subtle spookiness, not startle-scares or violence. This is admirably non-violent - and well-acted - but really just one "Boo!" after another. Written by Leigh Whannell - who wrote the clever and exciting Saw - and produced by Jason Blum - who worked on the top-notch Paranormal Activity - Insidious basically steals the plot of the latter and strips it of every bit of restraint and subtlety. In fact, there isn't an original moment in it. By the time the Eccentric Exorcist showed up, it was just one cliche too many and I was thinking, "Gimme a break."
It's not awful or anything and if you want your girlfriend to jump into your lap every ten minutes, it might be fun to watch on video. But if you're looking for the narrative drive of The Ring, the character depth of The Sixth Sense or the creative story telling of Paranormal Activity, you can pretty well take a pass on Insidious.