Coming back from Washington/Dulles yesterday on the day flight we made our way up the east coast at 41000 and somewhere north/east of Boston began to pick up some light turbulence. The solution? Descend to 39000! I think one of the benefits of transatlantic flying these days is that there is some flexibility in level assignments which means that if you do pick up some turbulence the pilots can sometimes (not always) get out of it by requesting a different flight level.
Thinking about it, I reckon you're more likely to get turbulence eastbound. Why? Because the airlines try and take advantage of the prevailing wind in the jetstream and fly in the jetsream to get the tailwind and that stream, like a water stream that flows quickly, tends to have more turbulence than a calm, slow flowing river. Going west they try and keep out of the jetstream because it causes a head wind which slows them down. However, based on yesterday it seems to me that they are getting better at avoid the turbulence when it does occur.