Earlier quoted context omitted.
If you want to create Mac OS X apps, forget about multi platform stuff - your customers do not care if your app runs on other platforms, and they will ignore your app if it does look and behave like a great Mac app.
It is a universal Gui API. So on OS X it api's to carbon (soon to be cocoa.) On windows it api's to mfc and on linux to xwin. So yes, it has exactly the same look and feel as a mac app or whatever platform you choose build on. Once it's compiled it's just a bunch of native system gui calls so there is no way to tell the difference. You've probably used Qt a million times and not known it. Opera and Google Earth are b…
Opera and Google Earth are good examples of such apps - they suck. Both have non native and ugly user interface. So if you your app does more or less what other apps do, but looks like this, people will prefer the native cocoa apps.