Research In Motion's PlayBook went on sale in the United States and Canada on Tuesday in a launch the company hopes will win customers away from Apple's dominant iPad tablet computer.

But customers trickled in slowly at stores that opened early, in comparison to the throngs that flocked to stores when the iPad 2 was introduced a month ago.

At a Sears department store in downtown Toronto, just five people showed up for the 7 a.m. opening.

At an Office Depot store in Midtown New York, three PlayBooks left the shelves within 20 minutes of the store opening, while not a soul stirred outside a nearby Staples store.

The stakes could not be higher for the Canadian company, whose BlackBerry smartphone once reigned supreme but has struggled to compete since Apple's iPhone and a slew of devices running Google's Android entered the fray.

Reviews have panned the WiFi-only PlayBook for lacking RIM's trademark email and organizer applications; it needs a BlackBerry to access those.

But retailers, including Staples and Best Buy, say solid orders suggest pent-up demand for a capable alternative to the iPad.

"Some of the complaints they had don't really apply to me, like not having native calendar and email doesn't matter because I've got a BlackBerry and I'm going to have that everywhere," Andre Cousineau, a 34-year-old working in banking, said as he picked up the new device in Toronto.

Some 20,000 stores across the United States and Canada were to stock the PlayBook, and it will also be sold directly to businesses.

Apple, which established the tablet market a year ago, sold almost 15 million iPads in 2010; RIM is expected to move 3 million PlayBooks in a similar window in 2011, according to 18 analysts polled by Reuters.

"It's not going to be in the same league as the iPad," said Al Hilwa, a Seattle-based analyst at IDC. "The question is will it sell more than the Xoom but less than the Galaxy," he added, referring to Android-based tablets from Motorola Mobility and Samsung.

Staples Canada ditched plans to open its doors at midnight in favor of a 7 a.m. start, underscoring the challenges in creating the buzz typical of an Apple launch.

Steve Coffin, operations manager at a Future Shop in downtown Toronto, said orders for the PlayBook lessened morning lineups, because shoppers were guaranteed a device.

"Based on those numbers coming in, we expect it to be successful," Coffin said shortly after the store opened.

"When you know you've got a guaranteed copy, people are coming in on their way too work," he added. "We expect to have people coming in on their lunch hour."