Speaking for the older Rockets... I've had the pleasure of riding in the rain on many occasions and displeasure of riding in the snow once. I found my girl very stable. That said, I run Avon Cobra/Cobra Chrome tires and am a bit more gingerly on the throttle in bad weather. The OEM Metzler tires were junk and I would slide on crosswalk paint when it was dry as a bone out. I had no issue with handling or with water getting in places it shouldn't. That said, I'm running the OEM air intake plumbing so can't speak for those with the upgrade. I also utilize engine braking a tad more than normal too. Since I'm or an R3T, I have full size windscreen which is a huge help.
-MIG