Agree that the bulkeads make a big difference and makes it much more tolerable. With that said, if you are broad shouldered and over 6 feet tall, do not expect to be able to lie on your stomach/back on the 767 even at the bulkead - you have to sleep on your side. The coffin "closes in" the further up you are in the seat so there isn't enough room for your shoulders. I don't have this issue with the A330s as much.