Diehard fans mobbed Apple Inc stores in Europe and Asia as the iPad went on sale outside the United States on Friday, with some shoppers having queued all night to buy one of the coveted tablet computers.

The device, a little smaller than a regular notebook computer and with an open, color touchscreen, is designed for surfing the Web, watching movies and reading, and has been hailed by the publishing industry as a potential life-saver.

Apple sold a million iPads in the United States in the first month after its April 3 debut, exceeding the most bullish pre-launch estimates. Demand was so heavy the company delayed the international launch.

RBC Capital Markets estimated iPad's total shipments will reach 8.13 million units worldwide by the end of the year -- which would translate into at least $4 billion in revenue.

I wanted to touch it as soon as possible. I felt real excitement when it was finally in my hands, said Takechiyo Yamanaka, 19, who had camped out in front of Tokyo's flagship Apple store from Wednesday evening to be the first in line.

It's a bit of a gut decision, an emotional decision, because it's not really rationally justifiable, said Anna Kistner as she emerged from the Apple store in Munich, Germany with two iPads. It's a lot of money.

The iPad is now on sale in Germany, France, Italy, Switzerland, Spain, Britain, Japan, Australia and Canada.

Prices for the cheapest, Wi-Fi only version range from $499 in the United States to the equivalent of $617 in Britain.

The buzz around the iPad helped propel Apple past Microsoft this week to become the world's most valuable technology stock, marking a remarkable turnaround of a company that nearly went out of business in the 1990s.

Apple shares were up 2.2 percent at $258.99 before the market open in New York.

CREATING A NEED

Apple now gets almost three-fifths of its revenue outside the United States, and it is counting on its base of fans who already own an iPod, iPhone or Mac to add the iPad to their collection, as rivals line up with their own tablet offerings.

Pascal Lordon, among the first in line at the flagship Apple store underneath the Louvre in Paris, said he already had all Apple's other products and described himself as a big fan.

The iPhone created a new need but the screen is small. The iPad is more comfortable -- it has a real screen, said the 51-year-old, who works in video editing.

Dell's Streak tablet computer will go on sale next month in Britain. Sony Corp and Hewlett-Packard also have tablets in the works.

I'm not going to buy the iPad now as it's expensive. And I'm a Sony fan, said Kengo Nakajima, a 19-year old college student who waited in line with his friend Yamanaka at the Apple store in Tokyo's Ginza shopping district.

Amazon, whose Kindle e-book reader could be seen as a rival to the iPad, said it would be offering its Kindle iPad application in all countries where the iPad was now on sale.

Analysts at research firm Informa Telecoms & Media said they believed most iPad sales would be of wi-fi only models, citing the limited case for outdoor usage, higher prices for 3G models and the ability to tether the iPad to a mobile phone as reasons.

At London's Apple store, a circus-like atmosphere prevailed.

Jake! Jake! Jake! store staff chanted as Jake Lee, a 17 year-old student who had waited 20 hours, entered.

British actor and technophile Stephen Fry said Apple had proved the skeptics wrong. Whenever Apple comes up with a new product, the initial response... is always negative, because no one can quite believe it can happen again, he told Reuters.

SUPPLY CONSTRAINTS

Apple has yet to announce a launch date for mainland China, which could prove a much more difficult market to crack. Bootleg versions of the gadget are being snapped up online and in retail malls in the piracy-prone country.

However, there is some concern that Apple, which contracts out the production of the device and depends on numerous parts suppliers, may not be able to supply enough of the device.

There's still going to be supply constraints, but I'm expecting them to sell every single thing they can ship, Andy Hargreaves, a U.S.-based analyst at Pacific Crest Securities, said ahead of Friday's launch.

Retailer Best Buy said it was restricting sales at its two British outlets to one iPad per household.

Michito Kimura, a senior analyst at market research firm IDC Japan, said the test would come after the honeymoon period.

The real game will start after 'core users' have the devices. I imagine a price cut may be necessary before the Christmas holiday season to stimulate demand.

(Additional reporting by Alexei Oreskovic and Edwin Chan in San Francisco, Jens Hack in Munich and Valle Aviles in London)

(Writing by Georgina Prodhan; Editing by Hans Peters)

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