New York, Apr 4 (DPA): After months of hype, speculation and anticipation Apple's iPad tablet computer went on sale Saturday hoping to spark a mainstream change in digital devices.

The sleek monitor, which is controlled mainly through touchscreen gestures rather than a mouse and keyboard, went on sale at Apple stores around the US and at branches of the leading electronics chain Best Buy, as well as through Apple's website.

Long lines of customers eager to be among the first to get their hands on the iPad waited for stores to open across the US, and analysts expect supply shortages to lead most stores to sell out within hours.

Some customers came from Cyprus, Spain and Argentina to snap up iPads which don't go on sale internationally until the end of the month. Hundred of people lines up overnight to ensure their purchase.

"I just got to have this product, man" Luis Hernandez, a 30-year-old artist, told TV reporters outside the Apple shop in New York City's Soho district. "I can't wait to try out all the apps and functions."

Apple is expected to sell between 200,000 to 300,000 iPads on the debut weekend with some forecasts predicting total sales for 2010 at around 7 million units, driven by early adopters and other users attracted to the device's intuitive touch-screen interface.

The first units, which come only with the ability to connect to the web over wi-fi, cost $499. iPads capable of using 3G phone networks will be available at the end of April and will cost up to $829.

Apple is positioning the iPad as the perfect casual computer to fill the space between traditional laptops and smartphones, and many publishers are hoping that its success will allow them to start charging for internet content specially formatted to take advantage of the iPad's unique qualities.

The device is compatible with the thousands of Apps designed for Apple's iPhone, and the company is hoping the iPad changes computing habits in the same way that the iPhone sparked a revolution in smartphones following its 2007 launch.

Reviewers have been largely positive about the iPad. Tech guru Walt Mossberg of the Wall Street Journal said "it has the potential to change portable computing profoundly, and to challenge the primacy of the laptop".

"It could even help, eventually, to propel the finger-driven, multitouch user interface ahead of the mouse-driven interface that has prevailed for decades," he wrote.

The New York Times' David Pogue castigated the device's "horrible" touchsceen keyboard, its incompatibility with Flash videos, and its inability to multitask. But while he said the device was unsuitable for techies, he recommended it for other people.

PC magazine also noted the devices drawbacks, but praised it as a "gorgeous, slim slate, with a beautiful touch screen" and called the iPad a "winner that will undoubtedly be a driving force in shaping the emerging tablet landscape."

"Apple has pretty much nailed it with this first iPad, though there's certainly room for improvement," wrote Ed Baig in USA Today.