Mar 14, 2011 11:15 GMT  ·  By

A research note signed Gene Munster, an analyst with Piper Jaffray, reveals that iPad 2 is doing wonders at expanding Apple’s userbase, while leaving researchers in the dark as to just how many units Apple sold during the tablet’s first weekend.

Although he cannot put his finger on these estimates, Munster says Apple sold 400,000 to 500,000 iPad 2 units in day one.

Should the whole weekend count, Apple may have well sold double the amount of iPads delivered last year, when the original tablet debuted.

The iPad 1 sold 300,000 in its first weekend, and we can expect the makers to issue an official report today, confirming double the amount of tablets sold this time around.

According to Munster, the sheer number of new buyers was particularly significant.

"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,” Munster said, according to Fortune.

The Piper Jaffray analyst surveyed 236 people sitting in lines to buy the iPad 2 at various stores.

He signaled that, “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."

According to the same report, Deutsche Bank's Chris Whitmore corroborates Munster’s claims in that pretty much every store carrying the iPad has sold out completely.

After calling about 100 stores, 50 of which were Apple’s, Whitmore could say with certainty that there were no iPad 2 units in stock.

"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," he said.