Utterly brilliant. Sharlto Copley was utterly superb.
The only thing which let the film down was the disc itself - as with so many from LoveFilm it was very grubby, and died completely at a crucial bit near the end when [SPOILER] happened. Had to skip a bit, but got the gist.
Did I mention how good Sharlto Copley was? Cor. And he'd not acted before, apparently. Let's hope he keeps it up. That boy will go far.