It's actually quite good. My initial feeling was that it was much longer than it needed to be, but I've put that down to the fact that I had a splitting headache and felt quite sick at the time. I think maybe the problem was that I was expecting it to be a full-on action movie focusing almost entirely on the titular three days, and it's not. It's much cleverer than your standard action film, and spends a lot of time with Crowe preparing for those three days. I just didn't expect that, but I feel it was crucial to the film. It would have been hollow without it.
Elizabeth Banks seems a bit underused as Crowe's imprisoned wife, she seems more of a plot point than an actual character, and the blink-and-you'd-miss-it appearance made by Liam Neeson was a bit of a shock. I remember seeing him in the trailers when the film was first released, and expected him to be in the film for more than the thirty seconds that he is. I kept waiting for him to show up again, but he never did. Olivia Wilde makes a couple of appearances as well, and I expected her character to play a bigger role, but really Crowe has to carry the entire film by himself. I was quite impressed by him, but then I am possibly the last person left who hasn't seen Gladiator.
I'd definitely recommend this film because it's different. It's an action movie with a bit more depth than is usual, but there's some comedy in there, too. I really was quite impressed.