FWIW, when I flew on the new config. 747 UD a few months ago, and from exploring around during the flight (FRA-IAD) I would've picked the front right seats adjacent the lav (sorry, I don't know the row # offhand). If offered the most privacy (no adjacent seats) and it was nice and dark up there with all the shades drawn. I also never noticed any lines or mingling going on, although I'm sure there was a flush or two that may have been annoying.

We sat in the next to last row towards the rear, on the right (16H/K I think?) and it would've been fine although there was a little more FA traffic being closer to the galley, and the family across from us on the left side had a lap child that was going NUTS the whole flight...running around, screaming, etc. Plus they never pulled their blinds.

YMMV of course!

Craig