Jeff Bridges does a great acting job and the music is fun, but the plot is weak. It's completely unbelievable that Maggie Gyllenhall's character would be attracted to Bad Blake, who is near the bottom of his alcoholism when she meets him, not to mention that he's twice her age.
Putting aside that implausibility, the story is flat and plot-by-number. I see I'm in the minority of reviewers here, but five of the seven people I saw this with agreed with me.