If I enable the new WikiText Editor on English Wikipedia and click the "edit" tab on the Barack Obama article, it does nothing (besides changing the URL). I don't get an editing interface or an error (even in the console). It just continues to show the Barack Obama article as if nothing had happened.
@Ryasmeen: I don't know how you got to that URL. If you click the edit button, it should have sent you to:
Maybe you have some special gadget installed that strips editintro templates?