I flew FRA - ATL on DL 15 yesterday on a 764 with the new seats.
At first, they felt pretty narrowed, but after I while I must say I really liked them. The fully-flat position is great if you are a side-sleeper, and I found the large armrest to be very handy. I also really loved that now you can have a window seat AND direct isle access.
Looking forward to my flight back on friday with the same seat config!