I just came back from 281/280 ATL-NRT-SIN and rt last week.
As others have said, the DL lounges are probably some of the best in the system. Great views, food, the legendary beer machines, macs, showers, etc. Security takes no time at all.
I've done 73A on the 747 in the past, but I've never slept as well as I did on the 777LR. One suggestion, thought it really depends on personal preference, is to sleep in the opposite direction. When I put my seat into the bed mode, I found my head to be lower than my feet, even with the BE pillow. Instead, I now sleep with my head on the footrest (closer to the aisle) which elevates my head above my feet due to the angle in flight. I find it much more comfortable than the normal way.
Also, the row 7 and 14 window seats in BE have a small shelf next to the seat which gives you a little more space. Quite nice to keep a small bag or random things there...