Just watched "31" the other night from Rob Zombie
Saw this too, I'd give it a 5.5 - 6. It's not a great film, but a fun time waster. Very basic "Most Dangerous Game" or "Running Man" plot mixed with 70's style gore. I really like the way Zombie films his original films, he's pretty good at capturing a grind house feel, but you can see the budget constraints on this one, small cast, limited scenery, etc.... Cast is pretty good, with the stand out being the main bad guy that shows up in the last 3rd of the film or so. As a side note, he'd make a fine Joker in a Batman film.
You may want to wait till the director's cut comes out in a few weeks, as it has many gore and sex scenes restored.
Another fine low budget film, was Gibson's "Blood Father". Very fine actioneer that proves Gibson still has it.