Ezio,

Your patch looks good, with these notes:

* When raising TypeError in the Python constructor, say that 'attrib' must be a dict, otherwise it's not clear *what* must be a dict.
* The 'attrib' keyword handling has to be added to SubElement too, as Markus said. I guess it would make sense to move it into some helper function to avoid duplication.
* The new keyword arguments have to be documented in the ReST docs of ET, since they haven't been documented until now