LOS ANGELES — Apple's tiny iPod Nano, expected to be the company's big hit this fall, has unleashed a firestorm on the Internet from customers complaining that their new units scratch too easily.

Additionally, Apple acknowledges that the screens on some Nanos have cracked and has agreed to replace the models with new units. The company says it hasn't received many complaints about scratches. "We do not believe it's a widespread issue," Apple spokesman Steve Dowling says.

But on Internet discussion boards and blogs, iPod fans — who usually enthuse about the design of the trendy digital music devices — are griping about a beautiful product they say doesn't look as good after it leaves the box. They talk of scratches on the screen and the body.

"I got my Nano a week and a half ago, and it was scratched within 30 minutes," says Tyler Hall, a Chattanooga, Tenn., Web designer who this week put up a site called nanoscratch.com. "I have three other iPods, and none have scratched like this."

Dowling says the plastic shell of the Nano is made from the same material used on other recent iPods. He suggests that if users are concerned about scratching, they should buy one of the many Nano cases that will soon be available.

"I don't want to spend $30 for a case. That's an outrageous amount of money to spend," says Mark Rickert, a Tampa, Fla., wedding videographer, who says his Nano screen became scratched within days of purchase. "I love Apple, but they dropped the ball on this one."

Apple attributes the cracked-screen problem to a vendor defect affecting "less than one-tenth of 1 percent" of Nano shipments.

Dowling declined to say how many Nanos have been sold since their debut this month. Securities analyst Charles Wolf of Needham & Co. estimates sales at 1 million units.

Wolf had projected that Apple would sell 5 million Nanos in the fourth quarter but says the controversy could end up costing the company some sales in the short term if Apple isn't more proactive.

"Clearly, Apple has to deal with the perception that is out there," he says. "This will clearly impact sales in a negative way, at least in the short run, until they address the issue."

However, Wolf notes that Apple has had problems with previous iPods — including shorter-than-expected battery life and units that jammed — that had little impact on sales. "A dead battery is much worse than a scratch, so I think they'll be able to ride this out," he says.

Wolf, who says he has a Nano that isn't scratched, thinks part of the problem is consumer expectations.

With the Nano, Apple introduced one of the coolest-looking products of the year, and "People want it to look as nice as it did when they first took it out of the box. That's not realistic."

Apple has a 74 percent market share of digital music players and has sold 27 million iPods.