I have to credit Matthew Weiner for doing a Q&A after the screening, because had he not done so and explained a bit more of what he was going for, I suspect this review would be less positive.
Let's start with the good: it is a dramedy that more often than not hits its marks, and both the dialogue and performances are strong. Owen Wilson is really good playing more of an asshole than you typically see him play, and Zach Galifianakis is funny without coming across as a cartoon. There's a number of great supporting performances from Amy Poelher and others, and aside from some contrived romantic subplots that don't make a ton of sense, everything feels pretty real and natural, which Weiner elaborated... was the point: to create something that feels like real life.
And that's why I'm inclined to give it some slack for not always feeling perfect - that's life, and maybe it's a bit meta to say that life isn't perfect so neither should be a film that reflects life, but I felt like Weiner accomplished what he said out to do and made something charming but not particularly memorable... I certainly feel like charming and unmemorable describes my life at more than a few points.
The only downside (and it's a biggie) is the score. For a film trying (and mostly succeeding) at being naturalistic in it's rhythm and tone, the score is the most cloying tripe I've ever heard, and every time it pops up it shatters any suspension of disbelief and turns the film into a sitcom. It's a profoundly bad choice that effectively derailed the movie for me, and I hope to hell it gets axed and replaced with something more subdued before the film sees general release. I try not to be prescriptive in my reviews because at the end of the day, I don't know how to make a movie, but this is one instance where an otherwise decent flick could be made much stronger with a single change.
And again, I'm talking about the music. There's more where this came from.