With the success of Apps on the Mac App store, such as Pixelmator, many devs are sizing up how they can port their existing apps over to OS X. Today with the release of Chameleon, developers now have the ability to port their existing iOS code directly to OS X. Chameleon is a byproduct from IconFactory, as they created this framework while porting Twitterific to allow for a direct port from iOS into OS X.
Chameleon is definately a work in progress, with 60% of UIKit having been ported so far. There are some notable missing parts of UIKit, such as the UITabBar and UISwitch.
Historically the mantra of write once, run everywhere has yielded some poor products, but I'm interested to see how I can leverage Chameleon and specifically how well that will perform on OS X.