No mullions. And I also agree with @elcieg about not using those cabinets for display. What are you planning to display there? If they are important artistic pieces, no one will be able to see them properly up there. Or, if they are tchotchkes cause you don't know what else to put there, I think you'd be better off having solid doors at the top row, and using those cabinets for storage of things that are not used frequently, but nevertheless need to be stored somewhere - holiday items, shelf liner, batteries, and the like.
I prefer instead to have a few of the bottom row of uppers be glass doors, not the smaller upper-uppers. In your pictured kitchen, you could do 4 glass doors that are over the coffee/toaster area to the right of the window, and store glassware in there and china. That accomplishes two things: (1) when people visit, they can get that stuff themselves, since they can see it; and (2) you are adding light and openness by reflecting the light from the windows next to them. No mullions on those either.
Q