I'm not going to go over the plot much because others have explained what there is of one pretty well. The movie has a lot of dead ends and leaves a lot of things unexplained. These, I feel, were the biggest weaknesses besides the attempt at creating atmosphere with a lack of lighting. Some scenes were spot on in their look, but many were muddy and lacked any detail at all.
A mediocre monster, general gore and acting that was a bit below pro-level all give away the movie's low budget roots. I feel all of these are forgivable though when you consider the short amount of time they apparently had to shoot and the small amount of money. While I'm sure there are many filmmakers who could have done more with $150,000 on a video production budget, I can see how it bogs things down.
Where budget shouldn't be a factor is the screenplay itself. Most of the time I wasn't quite sure what the hell was going on and by the end I just didn't care. There was something about a video game and a monster and a crazy kid who was now an adult. How the monster worked, what his particular powers were or how he chose his victims wasn't important I guess.
So, if you're watching a movie tonight to be scared witless, see Oscar winning performances by actors who had time to connect with their characters, grade-A special F/X or a deep story with rich, full characters, give this one a pass. But, if you like to see monsters dismember people you can fast forward to the fun parts.