Hey, just published my functional version of Nested Set support for model. Perhaps someone might want to use it. Its fully transactional and also locks records before update so noone can break your tree.
https://github.com/davihu/phalcon-ext/blob/master/src/PhalconExt/Mvc/Model/Traits/NestedSetTrait.php
Not fully documented yet, will do it later, I am currently very busy.
