I'm familiar w/development on Windows. I just purchased a Mac Pro and downloaded the OSX version. I notice the interface is quite different, for example where's the top level ribbon?
Is there some doc which explains the differences?
Unity uses its own GUI system for the interface, so there really aren't any differences, aside from having the ability in the preferences to use the OS X color picker instead of the Unity color picker (which I would recommend doing). I'm not sure what you mean by the "top level ribbon", unless you're talking about the menus, in which case the menus are always in the top bar for all apps in OS X.