I'm taking a look at tree2 for the first time. One thing I've noticed right off is the documentation, or lack thereof :)
Most of the documentation is in the wiki, except for the tld. However, three attributes aren't documented at all: value, var, and varNodeToggler. I'm guessing var and value work like any UIData component (and it should be simple to copy those into the tlddocs from dataTable). However, varNodeToggler doesn't have any non-code documentation that I could find. I'm guessing it's an object that implements some kind of isExpanded/isCollapsed functionality and acts accordingly when a node's visibility state changes. Also, the http://www.irian.at/myfaces/tree2NoNav.jsf example seems kinda lame (only one node visible).
