ETA: Slate's regular TV reviewer weighs in on the show here.
Bill's sense of command—a kind of charismatic paternalism—should seduce you into believing that three pretty women would sign up as his brides. He believes he's doing God's will by being fruitful and multiplying, but there are also hints that he married the first wife for love, the second for money, and the third for sex. Bill got hitched to Barb (Jeanne Tripplehorn) 17 years ago. At some point, after having survived cancer and having a hysterectomy, she allowed Bill to take a second wife. That's Nicki (Chloë Sevigny), who dresses like Laura Ingalls Wilder and shops like Emma Bovary. The youngest wife is Margene (Ginnifer Goodwin), who started out in customer service at the store and then became the baby-sitter.
A good part of the drama extends from their rivalries. By turns, they are supportive and competitive, passive-aggressive and aggressive-aggressive. Nicki taunts Barb, who controls the purse strings, as "boss lady"; Margene cheeses off Barb and Nicki with a high-decibel orgasm at the breakfast hour; both Barb and Margene have to negotiate the considerable ego of Nicki, played by the marvelous Sevigny with a kind of neurotic hauteur. Her performance is reason enough to check out the show.
Part of the show's appeal is that it unfolds in something of a David Lynch universe. While the adults go around with euphemisms in their mouths ("dang," "dumbhead," "go to H") and the kids worry about whether to make out at the drive-in, ashen Roman Grant stalks around with his bolo tie, his child bride, and his violent aura. He's a preacher and a gangster at once, a surreal shard of Americana. Even better are the clues that the show, among other ambitions, wants to be an inquiry into how to live. Take, for instance, a moment in the third episode, when Bill presents Margene with the car she's been pouting for. She squeals like it's Christmas morning, and he counsels, "Now remember, stewardship, not consumption, is the proper relation to material wealth."

Cathy Seipp and Louis Wittig both gave it positive reviews on National Review Online.
Seipp:
I've grown irritable with that common libertarian response to the anti-gay marriage argument: So what, I sometimes hear, if legalized gay marriage leads to legalized polygamy? to get this straight: this is the writer's p.o.v. -- against gay marriage, believes it leads to allowing plural marriage ... which is slavery of women and children, and therefore anti-liberty. (writer is libertarian?) ok, statement of how polygamy has inherent tendency to becomes this slavery~: If all men are expected to have many wives, and the geezers in charge naturally fear vigorous upstart competition, then the whole set-up becomes an inherently cruel and unstable gerontocracy.
The remarkably well-written and engrossing Big Love is no more in favor of polygamy than The Sopranos is in favor of mobsters. Instead, like its lead-in, the new series uses the dynamics of a bizarre but functioning suburban family to underscore tensions inherent in all families.
Mormons should have no reason to be offended by the series. The Latter-Day Saints — seen by Big Love polygamists as the enemy — come off in this show as in comparison almost actual saints, squarely law-abiding and responsibly monogamous.
When you see the real-life versions on talk shows, they all seem dumpy, pasty-faced and on the dole — like that ridiculous Tom Green (CNN article), who got in legal trouble a few years ago for marrying five underage wives and failing to financially support his 29 children.
Wittig:
Its sui generis hook is watching already thought-provoking characters navigate a social landscape as exotic as the surface of Mars. That the situation occasionally seems to perplex the characters as much as the audience only makes it better. Several episodes in, Nicki storms into the kitchen and growls at Margene, “Did you and Bill have relations before he brought you home for all of us to marry?”
“No! And I don’t think that’s any of your business,” shouts Margene back. Then melting in frustration, she wonders, “Is it?”Is it? You do want to find out.
The teenage Henrickson kids regard their situation grudgingly, and a trail of cinematic breadcrumbs will lead regular watchers to the possibility that even Bill may not be as into “living the principle” as he seems. (??cinematic breadcrumbs? into living the principle = into having multiple wives?)
In late 2004, amid a boiling gay-marriage debate, law professor Jonathan Turley argued the case for legalizing polygamy in a USA Today op-ed (no link - is this finable online?). But, he added: [The] day of social acceptance will never come for polygamists. It is unlikely that any network is going to air The Polygamist Eye for the Monogamist Guy.