Never flown one, but I have actually seen one in person. Refuelled a logger in Wyoming a few years ago, and watched him start up and fly away afterwards. While he was sitting on the ground with engine idling, the vibration was so bad that his head was bouncing around like a bobble-head doll. Not my idea of a good time. Hope it got better in flight. Correction, it had to get better in flight; no one could possibly withstand what I saw for any length of time.
It's not supposed to do that, just check out some videos online. It actually seems to be a pretty smooth ride when properly t&b'ed.
When stopped-parked the rotor blades go out of alignment (lead lag hinge) .... pause the video at 0:08 and you can see it
Once some rpm builds up they align and smooth out.
But Yeah ... between 0:25 to 0:50 there sure is a lot of "bobble" like you said
.