In October i was a pax on a flight from Newark to LGW and i was on a 757 and i think for about almost all of the flight we where in turbulence until we got to Ireland that was about 5hrs of being buffeted round but i think the worst part of the flight was there was no personal in-flight entertainment
just a little screen in the distance to watch.
The only problem with the 757 for long flights is that with the single aile if you want to stretch your legs theres not much space to do it especially if everyone else is doing the same thing