Evan, what you've done looks great. Have you had a chance to package this component up? I'd love to get rid of flexlib's treegrid with something that ... works.
Will/does your grid component properly handle drag and drop? Sorting? Changing the dataprovider and changes to the dataprovider? ... I grabbed these issues off of flexlib's issue tracker <http://code.google.com/p/flexlib/issues/list> . It might pay to check how your component handles things listed there. I personally have ran into numerous of them.
