Not as good as the third one was, probably about the same level as the second. Some nice scares here and there (though once again one of the better ones from the trailer isn't in the film!) and a great garage sequence.
I still like how every film has offered a slightly different take on what's really happening due to the likely poor research/googling from the characters. I find that more interesting than a definative answer would be (because, lets face it, there's no answer at this stage that wouldn't seem deeply silly if it tried to rationalise everything we've seen).
Oh, and whilst I liked how the Connect product placement was incorporated into the script, I'm fairly sure I shouldn't have come out with such a strange craving for Pepsi.