I also get this problem, and it also affects my L hand. In my case I'm certain it's due to Vibration White Finger Syndrome. I used to get it occasionally on other bikes. It's worse in the cold weather, hence heated grips and heated gloves and the Touratech wind deflector ( which works for me, if not for others ) The condition is associated with some other diseases and is essentially due to impaired blood flow to the digits. The OK medical term is Raynaud's Phenomenon. A purely descriptive title It is not Raynaud's disease unless all other medical causes of which there are too many to enumerate here, have been eliminated. The problem can be made worse as in my case by the taking of B Blocker medication. Noticeably if I relax my grip in the bars the problem definately eases. I would have to disagree with Mouse about Raynaud's phenomenon being able to cause gangrene. Severely impared circulation can definately occur, but it's due to the underlying disease causing the Raynaud's phenomenon.
I'm not sure about the carpel tunnel syndrome as a cause. Extension of the wrist is certainly likely to cause stretching of the median nerve as it runs through the canal, but this would explain why some peeps seem to have a problem which resolves when the position of the wrist is changed ie different bars, and why others get relief when using devices enabling them to hold the bar more lightly ie throttle control devices.
I'm not sure about the carpel tunnel syndrome as a cause. Extension of the wrist is certainly likely to cause stretching of the median nerve as it runs through the canal, but this would explain why some peeps seem to have a problem which resolves when the position of the wrist is changed ie different bars, and why others get relief when using devices enabling them to hold the bar more lightly ie throttle control devices.
)
before purchase, drove GS in monsoon conditions, 
and splashed past cars at a ton with more confidence than I'd had in years. 
Had no vibration on test bike, and have had none on mine since buying a year ago. Numb bum? There's something seriously wrong with your bike mate! 
And your impressions are at odds with all other reports about the GS. 
