600,000-700,000 iPads Sold Saturday; Longer Than Expected Lines at Apple Stores

The first analysts’ estimates of launch-day iPad sales are beginning to roll in and they’re impressive, to say the least. In a research note issued Sunday morning, Piper Jaffray’s Gene Munster, who had expected Apple (AAPL) to sell between 200,000 and 300,000 iPads on Saturday, said his prediction was likely off by more than half.

“We estimate Apple sold between 600-700k iPads (including online pre-orders which started on March 12th) on the first day (4/3),” he wrote. “It took Apple three days to sell a million iPhone 3GS and iPhone 3G’s, and 74 days to sell 1m original iPhones.”

Interestingly, Munster said that inventory is not quite as constrained as one would think given Apple’s decision last week to push some iPad pre-order shipments ahead to April 12.

“As of 7:30PM ET on Saturday night (4/3), 19 of 20 stores we called still had availability of all models, which is a positive for first day sales given Apple was able to fulfill most demand,” Munster wrote.

“In addition,” the analyst continued, “we noted longer than expected lines at the five Apple stores we surveyed. For example, at the 5th Ave Store in New York we counted 730 people in line at 9am (when iPad sales began) compared to our count of 350 people for iPhone 3GS, and 540 people for iPhone 3G.”