The Coens are like Soderbergh, they alternate between risky adventures and "commercial" projects. Only in the Coens' world, it is not so much a matter of commercialism but a matter of respect for the genre. Half of their films are profoundly layered, with a typical genre at the "bottom" and all sorts of annotation and commentary in layers on the top.
Its the same in abstract painting, the real stuff that is: to be good at distancing yourself from representational art, you have to master it before you leave it. So the Coens work on mastering a genre before they extend it (and goof all over it).
Naturally, their first project is a straight genre picture. Naturally, it is good (even excellent in its class), if not particularly novel.
Noir is an abused term. I think there are only two notions that are necessary. The first is the existence of a capricious fate, producing coincidences that toy with humans (usually humans). The second is the placement of the viewer (via the camera) in some sort of conspiracy with this fate. In some nefarious way, the viewer _causes_ some of these.
You'll have to decide whether a noir film made after the period in which it was developed can be enjoyed in the same way. It does necessarily carry some distance, the study rather than the intuition. But the hardest thing in noir is ending. These guys do it as perfectly as I know: the last vision of a dying man, watching something inconsequential but inevitable.