Q. What about the vibrations? Are they negligible? or do they creep in all the time - RC 390?

No it does vibrate. Mainly the entire body is made out of fibre to reduce weight power ratio in the engine. The battery panel which is clearly an risky place to keep in front of the petrol tank, will surely get vibrations with use. You will definitely see is intensity increase with time. Mirrors also become squeaky. So vibrations from engine will be felt at high speeds of over 80kmh. So don't expect a smooth peaceful ride on this bike

With the new RC model with the silencer. The vibrations are substantially reduced compared to the old model. The engine is surely not vibration free but not something a person would worry about. But still I would suggest a test ride.