Just created the tree grid extension, the tree grid is based on the Ext.grid.GridPanel and Ext.data.Store, so the most grid/store options are in place. I've also added per node paging and some UI enhancements.
The code is currently beta, so any feedback and/or bug reports are highly appreciated.
Description, demo and download page is here at
Since 24 october 2008 license changed from GPL v.3 to BSD