It's great counterprogramming for the summer.

Rating: 8/10 (23 July 2014)

First off, I really wish they had stuck with the original title "Can A Song Save Your Life?", because that's actually what the film is about. Begin Again makes little to no sense as a title, and seems to be taken from a hat full of torn up pieces of paper with intentionally vague movie titles. This same hat clearly was responsible for super vague thrillers named 'Paranoia', 'Deception', and the trifecta of films coming to theatres with 'If' in the title (What If, If I Stay, and If Only). It makes a movie more bland to have a bland title that has nothing to do with the film.
No one in this film technically "begins" again. In fact, Ruffalo's character goes back to his old life almost immediately, using Knightley's character as a way to weasel himself back into his old label. He doesn't use it as a new start, rather it's more of a do-over. Second Chance would have made more sense.
Most of my problems lie in the fact that I really hate the title. I hate that they lost the particularly original title for an extremely bland title. The film was anything but extremely bland, often choosing to take the harder path in storytelling. This is a romance, but not a straightforward romance. This is two broken people coming together, who just might end up with the people they were with at the beginning of the film. And that's completely OK, because of the way these characters are written. Ruffalo isn't some creepy old dude trying to bang Knightley. He's into her because of her songwriting skills, and not her body. In fact, for the majority of the film, we wonder if Ruffalo has even noticed that Knightley is hot. It's possible that has escaped him.
Knightley is surprisingly good in this. She's struggled getting recognition for her work in the past few years, often being overshadowed by her male co-stars. Her last great role was probably Atonement, but she was also good in Never Let Me Go, The Duchess, and A Dangerous Method, though you probably forgot all of those films. Here, she actually outshines Ruffalo, who is still quite good as a depressed, struggling record exec/divorced father. I have a hard time gushing over Ruffalo here, when I just saw him at his career best in A Normal Heart.
Adam Levine is surprisingly good in his supporting role. He does have some acting chops, and isn't a complete waste on the screen. Keener is always good playing a frumpy wife, divorced or not. Steinfeld is good, but probably wasted as a moody teenager. Corden is slowly breaking through in America, and this role is a nice role to add to his resume, though I doubt he'll be remembered for it.
It's great counterprogramming for the summer. It's not like anything else you'll see this summer, and it is dangerously different from other romantic comedies. I mean, it takes balls to make some of these choices, and I appreciate that John Carney doesn't take the easy road out.
As far as whether or not a song can save your life, I suppose the answer is yes, because as the film shows us, music evokes emotion. It can remind us of a previous event, or a different place and time. The right song at the right time can most certainly save a life. Even if your life isn't in danger, the right song can most certainly cheer up your day. The right movie? Those can stay with you forever.