A friend of mine is aghast at the critical acclaim for Sideways, the latest film from Alexander Payne. She’s upset because the movie is populated by characters who are self-absorbed, promiscuous, and willing to support each other in severe misbehavior.

I understand her objections, but I don’t think Sideways is condoning misbehavior. I believe we’re supposed to wince, and sometimes laugh, in dismay — and even in affection — as these characters, who do have their strengths, blunder their way into all kinds of trouble. And beneath all of the tomfoolery and trouble, these characters have beating hearts and redemptive qualities as well.

The story of Sideways follows two friends, Jack (Thomas Haden Church) and Miles (Paul Giamatti), on a road trip during the week before Jack’s wedding. Miles wants to enjoy this last “guys’ week out” by touring wineries and savoring life, even as he groans over his failure as a writer and his disillusionment with love. Jack, on the other hand, wants to spend the week getting laid with any woman who will give him the time of day.

These are not characters we admire for their morality. They’re fools for whom patient viewers will develop some affection. We hope to see the Connoisseur and the Neanderthal learn something before it’s too late. By the end of their reckless and problem-prone journey, one of them clearly hasn’t learned a thing. The other, well . . . let’s just say there’s a glimmer of hope, but not much.

Coming after Election and About Schmidt, Sideways is the first of Payne’s films in which we have the chance to really care for the characters, because he reins in his strident satire better than before. We laugh in dismay and sympathy more often than we’re asked to laugh in contempt.

Still, it is true that Payne continues to express contempt for certain varieties of people, while showing an extravagant measure of patience and grace toward his snobbish, self-absorbed “heroes.” (There is a scene late in the film that is its most outrageous, but also its most cruel.) As in About Schmidt, the characters that he sympathizes with get special treatment, while those who are more simple-minded are also portrayed as despicable beasts. This is a disappointing weakness in a film of surprisingly warm, human, and insightful moments.

One of the two remarkable strengths of the film is Paul Giamatti’s performance. Giamatti just gets better and better with each role he plays. I loved him in last year’s American Splendor, but he’s even better here as Miles, who, like some fine wines, may reach his life’s “peak” later than most others do.

And he’s working with a fantastic supporting cast, including Virginia Madsen in her most radiant performance, playing the one woman in the world who speaks Miles’ language.

Thomas Haden Church is also strong as the thick-headed Jack. Jack is as dangerous and destructive in his reckless ignorance as Jude Law’s Closer character is in his malevolent selfishness.  He’s a despicable character portrayed in far too forgiving a light here. But while he’s insanely promiscuous and heartless toward women (especially a winery worker memorably played by Sandra Oh), he does at least try to muster some understanding for his despondent friend.

The other virtue of the film is Payne’s delicate use of wine as a metaphor throughout the script… a wonderful way of phrasing what he wants to say about human beings.

This is a film that offers some quiet insight. But you may find that, despite moments of sweetness and wisdom, the characters’ misbehavior leaves a bitter aftertaste.