Gonzo’s review published on Letterboxd:
The Good: Mesmerizing performance from Oscar Isaac. He absolutely owns the role and damn can he sing. John Goodman is also amusing in his cameo as a grumpy jazz musician. Cinematography is beautiful, which is no surprise since it's from the same guy who shot Amélie and Across the Universe—Bruno Delbonnel. Soundtrack is fantastic. Best soundtrack of the year. If you're a fan of folk music (like me), I'm pretty sure you'll love it. It also turns out that Oscar Isaac himself wrote the songs, which makes it even more amazing. (If he gets nominated for both Best Actor and Best Original Song, which he will, will that be a first?)
The Bad: The Coens' trademark dark humor, cynicism, and oddball characters are still present, so worry not. However, what Llewyn Davis lacks is the spark present in their previous films. If you're not into folk music, you might find it a long hour and forty.
The Bottom Line: Llewyn Davis is most certainly not a bad film, but it isn't that great either. At least it isn't too polished and mainstream like their last effort. But whereas True Grit was perhaps the Coens' most accessible work yet, Llewyn Davis is the complete opposite. I don't see this playing well with the casual crowd. I'd place Llewyn Davis somewhere in the middle of their filmography. Worth a look.