Apple's sold 450,000 iPads as of today, pushed 3.5 million iPad app downloads (update: 50 million iPhones!)
There you have it -- according to Steve Jobs at today's iPhone event, nearly half a million iPads have been pushed so far alongside 3.5 million iPad app downloads -- a perfect few orders of magnitude above the 3,500 iPad apps presently available. It's not clear whether that includes units sold to third party retailers (like Best Buy) that are still sitting on store shelves, though, so there's quite a bit of potential for variability there. Separately, he's mentioned that 50 million iPhones have now been sold worldwide alongside 35 million iPod touches -- so yeah, needless to say, the iPad has some big shoes to fill if it wants to hit the same level of rousing success.