I wished I liked "It Follows" a little bit more that I do. I loved the first two thirds of it. It's a wildly original and scary concept that breathed new life in a tired genre, and mostly got put to good use.
Unfortunately, the last third runs out of steam and bite, and I couldn't help but question the reasoning behind the way our main characters though they could destroy "It". Maybe the point was that child like innocence was the way to conquer what is essentially a sexual transmitted supernatural killer, but it doesn't quite come across with the "rules" that the film established previously. So for a portion of the film, I was angry at a bunch of idiots who put themselves in danger for a scheme that obviously wasn't going to work.
Still, this is a very good movie that you should watch, as with any new horror IP that actually makes an effort.