Data Tree and rTree are both commercial tree controls for LiveCode and licences for each can be bought through RunRev's marketplace (http://www.runrev.com/store/
). More information about Data Tree can be found at http://theworcestersource.com/DATATREE.aspx
I'm sure that our respective users will be able to come up with a list of pros and cons for each products but for me, I think that Data Tree focuses more on matching the host operating system whereas rTree focuses on being able to handle trees with many thousands of nodes (Data Tree limits the display to 1,200 nodes). Whilst both controls take slightly different approaches to coding and usage within projects, they are both very easy to work with.
Data Tree has recently been acquired by NativeSoft (http://www.nativesoft.net
), the developers of NativeGeometry and NativeDoc and development of a more advanced version of the control is in progress.