oh, the real thing would be to also provide an exception interface, so that you can catch any exception really. 
https://github.com/doctrine/phpcr-odm/blob/master/lib/Doctrine/ODM/PHPCR/PHPCRExceptionInterface.php

need to go now, will look into this tomorrow.

and i think its a sign we get ready to release when we micro-optimize on the exceptions :-)