It's quite difficult, if you start thinking about budget restraints and stuff like that. If the marketing campaign or friends have thrown things at you, that you actually have to put into the rating. If you consider the low budget of this movie, you should cut it more than a little bit of slack ... but should you really? Or should you just rate what you see and feel?
This of course is up to you. And as long, as you know what you are getting yourself into, everything is fine. This is quite a promising effort, done by the director. It has quite a few flaws (some of them can be recognized as "they did not have enough money", some not) and is not as suspenseful as I thought it would be.
It is on the other hand, quite fresh and will be very popular by people who actually care about "small movies", hype and anti-commercialism. Does that apply to you? The story is not entirely new, but hasn't been done that often. The main actor is quite good, but his "role" is limited. Give it a chance if you like, I hope the director will come up with a better project next time. The make-up effects were great .. especially considering the budget, but even without thinking about it!