Last year I traveled from BOS to SYD via LHR. I was in coach and I did not mind the trip at all. Part of the trip I had an entire row of seats to myself which was pretty nice since it enabled me to sleep fairly comfortably. However the rest of the way I was on a very full plane. I suppose it really depends on how uncomfortable you are when you are in coach normally. I find coach very comfortable, but I am only 5'3.