Summary Box: Apple’s much-anticipated iPad goes on sale as customers line up to be among first

Summary Box: Eager customers line up for iPad

THE PRODUCT: The much-anticipated iPad, a new class of tablet-style computers that went on sale Saturday.

THE EAGER CUSTOMERS: Scores waited in long lines across the country to be among the first owners. They seemed willing to buy first and discover all the uses later.

THE CHALLENGE: Apple must convince the rest of us of the need for another device that serves many of the same purposes as existing smart phones, laptops, e-book readers, set-top boxes and home broadband connections.