I have commited the keyboard navigation into the SVN. Please add lxlaucher-enable-key=1 in the gtkrc to enable this feature. All gtk notebook keys are useful now. Here is summary
* up/down/left/right can be used to move the cursor between tab and items in the panel.
* Enter can be used to execute an item or enter a folder.
* ctrl-pgdn and ctrl-pgup can be used to switch the tab
* ctrl-home and ctrl-end can be sued to jumpt to the first and last tab.