Novell's MonoTouch product has been released. MonoTouch is mono for the iPhone.
This allows compiling .net applications to native code and deploying to the iPhone.
There are akready 200 apps in the app store using Mono via Unity so the underlying technology is fairly well tested. MonoTouch adds Cocoa support and integration into MonoDevelop.
MonoTouch has 2 main issues for some users, the $399US price point, and the logo.
The price has disappointed a number of beta testers and the logo is the second worst I have seen recently (worst is the Toastmasters goatse).