I spent 4 days on a 2012 rental shark nose that had 87 total miles on it when I started. 
Could not let go of the bars with the cruise on or at any time...it would go into a head shake.  Down hill I could feel it start if I just relaxed my hands on the grips.  It would start out mild and    go to full on tank slapper if I would have let it.  I was renting with three other guys and they all had Ultra rentals.  After the first day of riding I was telling them about it.  One of them didn't know what I was talking about so the next day going down a mountain I pulled up next to him at about 35mph, let go of the bars, and let it build up to "not quite" a full on tank slapper.  He couldn't believe it!  Nothing that I could not control with keeping both hands on the grips and not letting it get started, but it was annoying.
I wanted to like it, it feels roomier for us big guys, but after 4 days I couldn't wait to get back to my Ultra.