It's either 'ahhh' or 'ugh'!

They are as ubiquitous as umbrellas on a rainy day. Or ants at a picnic. But they appear in a far more eye-catching array of colors. You've seen them on everyone from celebrities to toddlers. If you don't own them yourself, you undoubtedly know someone who does.

They are Crocs -- the trendy footwear reminiscent of an accidental mating between Swiss cheese and a gardening shoe. As their popularity has skyrocketed, Crocs have become the shoe that people either love, or love to hate.

"There's no in between," says Jackie Nelson, a Boulder, Colo., yoga instructor who has three pairs. "I'm a true Crocs fan, because I wear them despite their ugliness. You can't beat them for comfort."

Ugly shoes have long held a certain cachet. Think Birkenstocks, Uggs, Earth shoes. But few things are as fickle as fashion. As fads go, surely Crocs should be past their expiration date.

Oscar Wilde once observed: "Fashion is a form of ugliness so intolerable that we have to alter it every six months."

Crocs, however, seem to have cracked the code.

Footwear phenom

The company, founded in 2002 in Boulder by three fishing buddies, exploded into footwear fame around the time that Crocs went public in February 2006. A year and a half later, sales are stronger than ever: In the past year, they've jumped from $108 million to $364 million.

What was originally conceived as a boating shoe -- waterproof, with a nonskid sole and ventilation holes -- has become, in defiance of all reason, a worldwide sensation. Now available in 30 colors, the $30 clog-style shoe is made of a proprietary resin the company calls "Croslite." The light yet dense material yields a feel that fans liken to walking on marshmallows.

Comfort, apparently, appeals to a broad demographic. Fans include celebrity chef Mario Batali, actor Jack Nicholson and music stars Faith Hill and Tim McGraw. Recently, President Bush was photographed sporting black Crocs -- with black socks and shorts.

The Crocs phenomenon is not purely a love-fest, however. Detractors abound, and they aren't diplomatic. On Manolo's Shoe Blog, Crocs are termed "the hot trend in footwear for the lazy person." And on ihatecrocs.com, Vincenzo Ravina and Kate Leth devote an entire Web site "to the elimination of Crocs and those who think their excuses for wearing them are viable."

Ask Ravina why he finds Crocs so objectionable, and then take a breath. "They are exceedingly ugly. They are chunky, luridly colored, perforated and overall, an eyesore," he replies.

He and fellow blogger Leth have clearly struck a chord with their Web site, which they created a year ago on a whim and now gets at least 1,000 visitors a day. They do a brisk business selling T-shirts and buttons, with logos like "Friends don't let friends wear Crocs."

'Silly shoes'

Even in Boulder, where you can buy Crocs at the grocery store, there's something of a backlash.

"I don't have any friends who wear Crocs," says Rachel Losowski, a style-conscious senior at the University of Colorado. "They're just really bad. Really weird."

But at the Pedestrian Shops -- the largest Crocs dealer in Colorado -- sales of the garish shoes remain brisk. "We sell a couple of thousand pairs every month," says Richard Polk, at his sprawling store on Boulder's Pearl Street Mall. "We sell more Crocs on a summer day by noon than we do other brands all year long."

An element of whimsy accounts for much of Crocs' appeal. "The idea that I can do grown-up serious stuff and wear these silly shoes, that's fun," says Polk. "It's kind of like going to a candy store, but you don't eat it; you wear it."

While candy-colored feet may not be for everyone, Lyndon "Duke" Hanson, Crocs vice president and cofounder, has a ready reply for naysayers: Just try them on.

"We know there are Crocs bashers out there, but we can convert most haters," he says. "We say, 'We know they're ugly, but once you try them on, they're a thing of beauty.'"

Crocs is expanding its line. The company now sells more than 30 models -- all variations on the basic cloglike shoe. Come fall, a more stylish brand called YOU by Crocs will arrive in stores, featuring leather shoes and boots that incorporate Crocs resin.

Ravina thinks the fad will soon fade.

But Hanson is paying no heed to predictions of doom. "Sure, we had a one-hit wonder of a shoe, and we know that. But once you get to $5 billion, you're not a fad anymore; you've defined an industry," he says. "We're probably the most popular shoe in history."