It's, uh... it's good I suppose. I just don't know if I think there's really that much to talk about.
We don't know anything about these characters, we don't see much of what's happening to them, we just know they're running from Slender Man.
The video seems fairly influenced by the games, which is definitely something I would try to avoid, but that doesn't make it inherently bad. The fact that the video cuts around a lot makes it sort of difficult to follow the action- I'm still not sure if someone got clear or if the Slender Man took all of them.
As for the Slender Man itself, I appreciated how tall it was, and also the tentacles. Clearly not just a guy wearing a suit over a morphsuit, though its joints and proportions were a bit conventional.
The short film was a good short film, very good. In the Slender Man circle, good short films don't get you noticed- you need slow build horror, detailed characters, new spins on things people already think they know.
Make another one with some more of that stuff! It could be brilliant!