Flew the return on the 787-800 which is quite nice, as well, the seats were comfortable, but there is no bar area as there is on the 789. Since there is only a functional galley with no bells and whistles between the front and back cabins, there didn't seem to be as much difference, but the mini-cabin definitely had noise from Economy.
I didn't notice the rows missing a window on the 789, but I'm pretty sure 3 and 4 have both windows (it was night both ways so I didn't really notice). On the 788 the last row of the main J cabin has only one window.