I just got done watching this and I have to say it was much more interesting than the trailer I saw gives it credit for. I have to say Jake Gyllenhaal is a master of strange characters. The character of Louis Bloom is one disturbed and creepy fellow who doesn't take no for an answer. I loved Riz Ahmed in this as he is pretty much the only likeable character in this whole thing. I do think Bill Paxton's role and talent were slightly underused. The build up through the film is messed up, but in a totally intriguing and well done way. It's hard to talk about this film without spoiling it for others. So go check this out and I promise you will enjoy it.
Side Note: It's interesting to see that the director is married to main actress Rene Russo and that he wrote two other movies I enjoyed (Real Steel) and (The Bourne Legacy.