I may actually attempt the TCB retrofit when I do my NBT retrofit.
You would get ARTTI with 6AM with TCB. Without it, you should still get 6UH RTTI as fallback on NBT, same as CIC has.
Besides all the features shown in the "New BMW 609 Professional Nav Overview July 2012.pdf" I posted above, there are many other things that are added or improved. iDrive Touch with Handwriting Support, Map AutoZoom on main map, not just side map, etc.