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(CNN) -- After lining up for hours, or sometimes days, Apple fanatics on Thursday morning started to get their hands on the iPhone 4, the latest gizmo in that company's line of trend-setting smartphones.

The iPhone 4 went on sale at 7 a.m. local time Thursday in U.S. stores, and at 8 a.m. local time in France, Germany, Japan and the UK.

At an Apple Store in Atlanta, Georgia, customers and Apple staff clapped and cheered when the store opened at 7 a.m. ET.

A 20-year-old college student named Seth Herren said he had been waiting in line at Lenox Square Mall since 10 p.m. on Tuesday.

At a flagship Apple Store on Fifth Avenue in New York, more than 600 people had lined up to get a device that some were calling the "Jesus Phone," according to CNNMoney. Vuvuzelas trumpeted. Fans cheered.

In London, Priscilla Lee and her brother, Alex, had come all the way from Dubai, United Arab Emirates, to get a spot at the head of the line for the new phone, which features video conferencing, a faster processor and a sharper screen.

The Lee siblings said they had traveled so far because they had to have Apple's new gadget on the day it became available. "I've got an iPhone and then my iPod Touch. And then iPod Nano. IPod Classic -- the list goes on," Priscilla Lee said. "Apple. What else to say?"

Gizmodo, a technology blog, pointed its readers to an iPhone app -- called Line Snob -- that helps iPhone line junkies know how long they will be waiting. Of course, as one commenter pointed out, you would need an old version of the iPhone to be able to use that app.

When Apple CEO Steve Jobs unveiled the new phone this month, he said the iPhone 4 is "the biggest leap we've taken since the original iPhone," which debuted in 2007.

The phone will cost $199 for a 16-gigabyte version and $299 for a version with 32 gigabytes of storage space for photos, videos, movies and apps.

The iPhone 4 has a higher-resolution screen, which Apple calls a "retina display" and says is better than anything in the industry.

It is about 25 percent thinner than the most recent generation of iPhones and features cameras on the front and back, which will allow video conferencing.

The phone comes in two colors: black and white.

Early reviews of the phone have been predominantly positive.

Some have criticized Apple's continuing policy of not running Flash graphics, websites and games on its products, as well as the company's deal to sell the iPhone only with an AT&T wireless network contract.

The size of the iPhone's screen -- at 3.5 inches, measured diagonally -- has also come under criticism. Several Android-based smartphones sport larger screens, which some analysts say are better for watching video.

The Droid X and the HTC EVO 4G, for example, both have 4.3-inch screens.

iReport: Are you getting an iPhone? Having trouble with your order?

Apple's popular phone also faces competition from Android-based smartphones like the Droid X, which Verizon debuted this week. Those phones run on a different operating system and therefore use different apps and games.

BlackBerry phones from the company Research In Motion remain the most popular smartphones on the market, although some analysts classify those phones separately because they run different apps and often don't have touch-sensitive screens. iPhones and Android phones are thought to be more popular with general consumers, while the BlackBerry has more business clients.

Aside from the potential mob scenes at Apple stores, three other retailers -- Best Buy, Wal-Mart and Radio Shack -- will have the iPhone 4 on Thursday.

The phones also were available for pre-order on the internet.

Some customers reported receiving the phones Wednesday, an apparent hat-tip from Apple to its most loyal customers. The company sold 600,000 iPhone 4s in pre-order, and one analyst expected the company to sell as many as 9.5 million phones by the end of June. That would break previous records set by the company. Apple sold 1 million of the first iPhone in about 2½ months.

Apple said the pre-order response for the iPhone 4 has been overwhelming, roughly 10 times bigger than the response when the 3GS went on sale. That led to some problems with orders and phone availability.

On Thursday morning, there was some tension among people who wanted to get their hands on the new iPhone.

Christopher Renshaw, 30, of Chattanooga, Tennessee, said he got in line at Atlanta's Lenox Square Mall at 2 a.m. on Thursday.

He said people were cutting to the front of the line, and that made him angry.

"I said, 'If you get your iPhone before me, I'll knock you out,' " he recalled.

Are you going to pick up an iPhone 4 on Thursday? Check out our CNN iReport assignment and tell us what you think of the phone. Or feel free to share your thoughts with us in the comments section below.

CNN's Eva Vasquez and Tasneem Anjarwalla contributed to this report.