BlackBerry 10 goes on sale in the U.S.

　　BlackBerry began a fight to regain share in the key U.S. market on Friday with the debut of the first phone running its BlackBerry 10 operating system.
　　The BlackBerry Z10 went on sale nationwide at stores of AT&T, the country's biggest cellular carrier. It's scheduled to launch at T-Mobile and Verizon stores next week.
　　BlackBerry 10 represents a complete restart for the company.
　　At an AT&T store on San Francisco's Market Street, in the heart of the city's financial district, there were none of the long lines and whooping customers that symbolize iPhone launches.
　　But no one really expected that.
　　As the store opened at 9 a.m., just one of three customers waiting in line was there to buy the BlackBerry Z10.
　　(See a video report from the AT&T San Francisco store launch on YouTube.)
　　But the individual, who declined to be interviewed, wasn't the only BlackBerry customer in the queue.
　　San Francisco resident Darlene Henderson was clutching her current phone, a BlackBerry Torch, in her hands as she spoke to a reporter.
　　"I'm upgrading and actually, I'm leaning towards the Samsung instead of BlackBerry 10," she said. "I heard about it, read about it, the reviews are great, so I'm waiting for my income tax [refund] so I can upgrade."
　　The choice of Henderson to leave BlackBerry represents one of the big challenges facing the company. The prolonged development of BlackBerry 10, which suffered delays and took more than a year to get to market, meant some users got impatient and have already switched to Apple and Android.
　　BlackBerry needs the Z10 and the Q10, a yet-to-be-launched handset with a physical keyboard, to be impressive enough to convince existing customers to stick with the platform. To that end, the company has poured millions of dollars into encouraging app developers to get applications on the OS to better match competitors.
　　Another big challenge it faces is signing up new customers.
　　BlackBerry doesn't have a chance of matching the momentum of Apple and Android any time soon, so it's in a battle with Microsoft for the third-place position in the market. Microsoft launched Windows Phone 8 in late 2012.
　　"We do know that there's BlackBerry loyalists out there who are going to love this phone," said John Britton, director of media relations at AT&T, speaking outside of the San Francisco store.
　　"We've seen lines -- obviously iPhones are the biggest lines we've seen. We've had lines for some other launches too," he said. "I think lately we've seen more people pre-ordering online. It's just an easier way to do it, it comes to them or they go to the store and pick it up."