Just how many Retina display-enabled apps are now available for the new iPad? Since Tim Cook unveiled Apple’s third generation tablet nine days ago, over 500 apps have received the upgrade treatment, according to an AppAdvice review of recently updated apps.

Through today, developers have submitted and Apple has approved 529 apps that are now Retina display-enabled. This is an amazing number considering Apple did not release to developers the tools necessary to upgrade until after the company’s March 7 iPad event.

To get apps approved, developers must make the necessary changes, recompile and then test the apps before sending them to Apple. And the number of Retina-enabled iPad apps will only grow in the days and weeks ahead. In fact, AppAdvice is still waiting for our AppStart for iPad app to get the Retina display treatment.

While this is definitely amazing news and quite a feat, original iPad and iPad 2 users should be aware of the hidden costs of Retina display.

If you want to see which apps have been updated to take advantage of the “resolutionary” display, click here.