Steve Jobs has just taken the stage at Apple’s iPhone OS 4.0 press event. Before getting to the anticipated product announcements, Jobs took the opportunity to highlight the immediate success of the iPad, which launched on Saturday.

As of today, Apple has sold 450,000 iPads — 150,000 more than total sales on the first day. That’s a phenomenal figure on the hardware sales side, but Jobs wasted no time celebrating some the iPad’s software accomplishments as well.

Here are the stats that Jobs is touting:

– Since the iPad launch on Saturday there have been 600,000 iBooks downloaded
– Over one million apps were downloaded to iPads on day one
– A total of 3.5 million apps have been downloaded to iPads since launch
– There are now 3,500 iPad-specific apps available for download, with 185,000 total apps available across all devices
– Total app store downloads, across all platforms, have surpassed the 4 billion mark