Actually, TreeView is what I have the most experience with. I choose it because Moodle includes YUI, but I found out that's pretty much it's only redeeming factor. It completely throws out any hope of accessibility or sane fallbacks, it has some nasty quirks (like the fact that TextNodes actually treat their 'text' as HTML), and the developers seem to screw things up with every update (misplacing the style file, secretly changing dependancies). Most of the bugs I had were due to YUI.
General developer forum
Interface design input please
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