This movie wasn't horrible, but it was not very good either. I got about what I expected when I rented it... a low budget sci-fi/horror movie that was at least somewhat entertaining.
Plot: C+, It starts out with a pretty generic, boring plot, but it grows into something more intriguing. I think the way they suddenly just dump the concept on you detracts from its greatness though.
Acting: C-, Acting was sufficient, but not great. They are about par with what you'd expect in a mediocre horror film. No one of the actors really stood out amongst the others as being exceptionally good, but one or two stood out as being exceptionally crappy.
Special Effects: C, Not that great, but again, it was sufficient.
Character development: D+, you don't really get attached to these characters. Part of it may have been the mediocre acting. The characters that stand out the most are the ones that follow the usual cliché character types. You have the tough guy, the smart computer nerd, the annoying goof-off joker, and more. The characters that didn't follow one of these cliché types really just blend into the background.
Best aspect of the movie: The actual concept they present to you later in the movie (I won't reveal) is interesting.
Worst aspect of the movie: Lack of character attachment. It's no secret people die in this movie, and when they do you'll find yourself not caring that much in most cases.