It is a rip off, but there isn't much originality on general when it comes to big Hollywood films and everything is based on tried and tested formulas, not straying too far from the plots, character types and techniques that have already been proved to work. Rip-oRAB and clones are a big current problem in the industry in general, and Repo Men is only obvious because it's picked on a quirky, low budget film as opposed to one of its box office fellows.