I'm pretty much in agreement with everything there. There are definitely some things I loved about the movie, but there were a couple of things that bothered me. The obviousness of the whole envelope switcheroo being one of them (but then again, even when you predict it, it can be somewhat satisfying, depending on whether or not you like the main character).
But I loved the "hankerchief as recurring villain" bits, and of course my favorite part of the movie was the fact that there was an anvil hanging in the shed. I was laughing hysterically when I noticed that, to the point where I think I was making other people in the theater nervous.
Ultimately, it's a fun little horror movie that doesn't try to be any more than what it is, and it works really well on that level. It's not quite up there with Evil Dead II or anything, but still a fun time. Definitely worth a rental if you get a chance...