I just got back from seeing this, and...
I definitely agree that that first shot of the hanging is very strong. It creeped me out and and made me brace myself for a terrifying movie. And it does deliver a few sharp jolts in the spooky night time scenes with a frightened Ethan Hawke investigating strange noises in his dark house.
But... The way the supernatural angle plays out totally sinks it for me... Spoilers: By the time the ghostly kids start running about the house, it becomes obvious what is going to happen. One of the Oswalt kids will become possessed and kill his family. The professor's and deputy's bits of exposition near the end are totally unnecessary, and by the end, you'll be going: "Oh, it was one of those ancient-Babylonian-deity-traps-possessed-child-on-Super 8-after-family-slaying movies..." It simply kills its own mystery - some iconic horrors need a whole franchise to accomplish that, but this one does it in just one movie. The final scare is a a real howler, by the way.
So for me, this is something of a misfire. Not as aggrevating as Drag Me to Hell, but I'd probably rate it lower than Insidious.