I usually love Steinberger's stuff, but I love Nossiter's stuff too. Plenty of Steinberger's criticisms are valid, especially the bit about its humorlessness - the book would have benefited from some levity, and it's odd that it's absent considering the book is mostly a narrative of people drinking wine, which usually leads to laughs and revelry. But, geez, if I had my druthers, Sarah Palin would be president and Ann Coulter would be Secretary of Defense, so if Nossiter's constant left-wing stink bombs don't ruin MY enjoyment of this book, they shouldn't pose a problem for anyone else, either.
The book is basically about how all the little discussions and debates we have about wine are microcosms for all those discussions and debates people have about Bigger Issues... and for him, a lot of those issues are political. (That's fine, because it's also a personal book, and if his politics are a big part of his thinking they are going to be a big part of this story.) If he thinks good wine is fundamentally leftist, you're free to make the opposite case (as I've done before) and you're free to argue that winemaking philosophy has no political content at all, but at the end of the day at least you've had the discussion, and that's what Nossiter is trying to accomplish. I think he pulls it off well.
The book is also about his attempt to come up with some language for talking about wine more meaningful than the tasting-note genre, and his frustration with the difficulty of doing so. That frustration makes him come off like a bit of a dickhead in a few scenes - even in his own account of the proceedings! - but he stays consistently insightful. Anybody who enjoys talking about talking about wine should read the book.