I decided to tend to the transmission and final drive of my GS to potentially do the first service of these units ever at 26k. They were both really easy and the splines were not rusted at all, although there really wasn't much moly lube on them and what was there had dried out. Pretty much like the ST, everything is straight-forward and makes sense, although it's interesting how BMW thinks compared to Honda. No idea what this would cost for a shop to do, but it's another task the average guy could do.
I drop mine down every 6K. Clean it up, check boots, , re-lube / new oil. Fun stuff....