Gene Munster’s team at Piper Jaffray walked the iPad 2 lines in New York City and Minneapolis and interviewed 236 would-be buyers. They also called various retailers (Apple stores, Target, Best Buy, etc.) looking for product. The results of their survey were released Sunday night. Their findings:

• Munster is sticking with his estimate of 400,000 to 500,000 iPad 2s sold, compared with 300,000 iPad 1s in its first weekend last year.
• The difference is that nearly all those iPad 2s were sold in one day; stocks were essentially depleted by Saturday and not replenished. In its calls to retailers over the weekend, his team was unable to find a single iPad 2.
• 70% of iPad 2 buyers were new to the iPad, compared with 23% of iPhone 4 buyers who were new to the iPhone at launch.

• Buyers were split almost evenly between Mac and PC users (51%/49%). By contrast, the split for the original iPad was 74%/26%.
• 47% of buyers were purchasing a 3G model, which carries a $130 premium.
• 41% purchased the 32GB iPad 2, up from 32% who bought the 32GB version of the original iPad. The 64GB models also gained a slight share. This means that the iPad 2’s average selling price (ASP) at launch was considerably higher than original iPad’s. (Munster doesn’t mention that at many outlets, Apple (AAPL) ran out of 16GB iPads first, then 32BG models, which may have been a factor pushing up the launch-day ASP.)
• 65% of buyers owned an iPhone, 24% owned a Kindle (up from 13% of original iPad buyers), but only 6% plan to read with their iPad (down from 19% in Piper Jaffray’s first iPad survey).
• 17% expect to use apps and play games, up from 9%, which suggests that the App Store ecosystem is growing.

The number of new buyers was particularly significant, says Munster:

“We believe this shows Apple is expanding its base of iPad users, which is critical to maintaining its early lead in the growing tablet market. As the user base grows Apple’s lead widens, and the company has a proven track record of building unmatched brand loyalty, which we believe will be a potent combination as the tablet market evolves.”

UPDATE: Deutsche Bank’s Chris Whitmore reported early Monday that his team called about 100 stores (50 Apple retail stores, 20 Best Buy and Wal-Mart stores and a handful of AT&T and Verizon stores) and got the same result as Munster’s:

“Our checks pointed to a shocking 100% stock out rate across Apple/authorized retail stores just a few hours into the official launch Friday evening, contributing to what we believe was one of the company’s most successful product launches to date.”

Below: The details of the Piper Jaffray survey:

[NOTE: Several readers have pointed out that the 28% and 32% in the first column of question 3 in the chart above make no sense. We suspect they were left over from question 1 and should have been replaced with NAs.]

Also on Fortune.com:

• Apple runs out of most iPads
• Video: Walking the longest iPad 2 line
• iPad line goes around the block in NYC

[Follow Philip Elmer-DeWitt on Twitter @philiped]