I believe there are some payload restrictions on the route, and they seem to prefer to restrict pax loads rather than their high-yield cargo, so you should have room to find a couple of empty seats and stretch out a bit.
I flew the A340 on AC across the atlantic in economy. Your flight will be longer, but you can extrapolate my experiences. I personally quite enjoyed my A340 flight. I found the seats very comfortable, much moreso than the 767 that I flew to YYZ to connect to the A340 with. There aren't PTV's in economy but personally I prefer the overhead mounted monitors anyways. I forget what the movie was on that flight, but I find AC usually has pretty good titles. Food was just fine, and flight attendants seemed pretty good about patrolling the cabin even during the overnight segments when most passengers were sleeping. I personally almost never sleep onboard aircraft, but the view flying over the atlantic was great, although at some points there was a bit of cloud. I found the aircraft quite smooth to fly on and extremely quiet, and I wouldn't hesitate to do it again. My only negative thing about it was that on the return trip I got quite badly jetlagged (the trip eastbound was absolutely jetlag free for me, actually).