I went in to Insidious with very low expectations. To my surprise, those expectations were exceeded. I was pleasantly surprised with this low budget old school horror film. The enjoyment factor was raised because Insidious is the kind of haunting movie I grew up with. Like Poltergeist or The Entity, the scares are organic, never relying on cheap thrills or CGI effects.
Insidious is the type of scary movie that is typically lacking in this era of film. Based on this alone, I think you should grab a copy and prepare yourself for a creepy ride.