Has anyone successfully installed and used NodeXL on a tablet (ASUS Vivo or Microsoft Surface) running Windows RT with the Office 2013 RT preview suite? 

I'm afraid that won't work, because NodeXL relies on some Windows technologies that Microsoft isn't providing for Windows RT.  You should be able to open a NodeXL workbook in RT that was created elsewhere and view its data, but you won't get a graph pane or a NodeXL tab in the Excel Ribbon.

-- Tony

Thank you for letting me know!