All depends on the seating configuration. We took Air France 777 CDG-ORD and the seats had ample pitch and leaned waaaay back, allowing you to actually rest comfortably, even in a middle. I took an AA 777 a while back LHR-ORD and it was not the same experience. In any case, everyone gets up and takes stretch breaks. We were able to get business seats on the way over to Europe last time we went which makes a huge difference on the way over because you can actually get a few hours of good rest.

Referencing the post above concerning the 737 to Hawaii from Denver, the 777 that UA flies on that route is configured for max density. Unless you have a premium seat, you are probably getting a worse seat than you get on a SWA 737. Ask anyone who has flown on it, it isn't comfortable at all.