Survey data seems to back up Gottheil's sales projection. According to ChangeWave Research, which in the first half of February -- days after Apple CEO Steve Jobs unveiled the iPad -- sales of the iPad will gain momentum for at least six months after launch.

Of the people polled who said that they are likely to buy an iPad, only 6% said they would put down their money in the first week after its release. That number climbed to 20% for two to three months after launch, and 23% for the four-to-six month period.

Paul Carton, ChangeWave's research director, cited the low number who said they would immediately buy an iPad to challenge the thinking of analysts like Gottheil and Marshall. "I don't think you'll see in the first weeks people pounding down the doors," he said. "It will take off slower, and build."

Starting on Friday, Apple's U.S. online store will accept pre-orders for both the WiFi-only and the WiFi+3G models. Apple's retail stores, however, will reserve only the WiFi iPad for pick-up on Saturday, April 3. The iPad will be available in late April in Australia, Canada, France, Germany, Italy, Japan, Spain, Switzerland and the U.K., Apple said last week.

Prices for those markets won't be announced until next month.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at or subscribe to . His e-mail address is .

in Computerworld's Macintoshes Knowledge Center.