The found footage genre is not for everyone, putting severe limitations on the way the plot is presented and what can be included. The filmmaker premise works very well, and Aaron's rising fear gives good reasoning for the expanding scope of what he records. Josef's desperate attempts to befriend him and erratic stalking work well. There are some suprises, red herrings and minor jump scares along the way, all adding to the atmospheric horror more than any special effects could.
The pace and real-world setting plant Creep firmly in the psychological horror camp. While my heart raced and my hair stood on end, it was not anyone in-film I was afraid for. Dangerous people who may or may not want to kill you are real, and the possibility that you are in danger with zero evidence to take to the police is the kind of logical adult fear that worries you in the early hours of a sleepless night.
When all the character driven tension is eventually resolved, the fact that things are actually resolved is more shocking than the jump scare. There's a little wrap up that confirms your suspicions and makes space for the sequels. Watch in the afternoon, and follow it up with some kitten videos, or watch it late at night with the window open to keep you from sleeping.