For the uninitiated, what do worn cush drive rubbers feel like?
Yes, as bmwroot says, if you hold the sprocket and wheel in each hand, you can see if there is any for-aft play in the cush rubbers... (almost certainly there will be) - there really shouldn't be any, but a 1/4" is bad, and half an inch is really
bad (in my opinion).
When riding, you may notice the wear though the rear wheel and transmission sort of pulsing/shunting - particularly under a steady throttle.
for info. as KTMmitch says above, when I asked the dealer about it while on my travels, they were more than helpful sorting me out under warranty overnight/the next day - top work BMW Las Vegas!
However, even the replacement rubbers soon showed signs of wear/slop - after just a few hundred more miles - and I resorted to sandwiching some strips of bicycle inner tube in there again at my next tyre change.
Ultimately, after another 7000+ miles of admittedly pretty hard on and off road riding, not only are the rubbers complete shot again, but I also now have side to side play in the sprocket carrier bearings - which is being dealt with at this latest service.
Basically don't let them go too far - if you have fore-aft play, get them swapped for new ones as soon as possible, and keep an eye on them otherwise the play can ultimately lead to wear in the bearings too.