I flew on the 787 from HEL-NRT and when the seat is flat it's not long enough for me to have my legs straight (i'm 6' 3"). This is a shame since otherwise the design is really nice and there is a thin mattress in the overhead bin to put on top of the seat.
I could sleep better with the seat on a slope and my feet on the floor.
I was in CX business class a few months ago and that was much better, it was much longer when turned into a bed.