With 3G iPad sales estimated at 300,000, Apple today announced that it has sold more than a million iPads since its US launch on April 3rd.

The 3G capable iPad went on sale in the US late last week, and analysts estimate that Apple has already sold 300,000 3G iPads, a number on par with the wi-fi only iPad launch.

And Apple announced today that it has passed the 1 million mark for all iPad sales after 28 days, which is less than half of the 74 days the iPhone needed to reach the same number after it was released. But unlike the iPad, the original iPhone required users to sign up for a new phone contract, which would account for the slower uptake.

The company also said that iPad users have downloaded more than 12 million apps from the App store and more than 1.5 million e-books from the iBookstore. Developers have also embraced the device, with more than 5,000 apps created specifically for the iPad.

Analyst Gene Munster said that he expects iPad sales to reach 4.3 million in 2010.

Both the 3G and wi-fi only iPads are expected to go on sale internationally at the end of May, after a delay due to strong demand in the US.