It's pretty atmospheric and well-written, some purple prose aside. A critique I heard was that it feels like it was written with a time constraint and spooky custard mouse was slapped on at the end to wrap the whole thing up quickly. I don't know how true that is, I just think it's one of those obligatory things. Sort of like how visual novels back in the day had to be porn otherwise they wouldn't sell, your creepypasta had to have a spooky mascot monster or else it wouldn't be popular.
Slimebeast may be obnoxiously sensitive to criticism but he's a quality writer. The sequel Room Zero is a significant improvement over the original, albeit a little silly at times.