I've been in the back of the ship twice, last time was in cabin 7625.
There was one day when the motion was really bad, but it was bad throughout the whole ship. The other times, it wasn't any better or worse than anywhere else on the ship.
Since you're at the end, there is less foot traffic and noise. We could easily go upstairs to the buffet or downstairs to the movie theater, internet cafe, etc. You didn't have to walk the length of the ship to get to a lot of areas.
I was a little apprehensive too, but it was fine and I liked the location.