I'm not sure why this has suddenly started, I've run the game in Windowed Fullscreen since launch with no noticeable issues, but about 2 weeks ago it started getting choppy. The FPS was pretty much the same as always, but the image just did not move as smoothly. Finally, today I tried Fullscreen and it's' about 100x better. Again, the FPS is about the same, but the picture is flawlessly smooth.
I have 3 monitors (and have since launch), not sure if that has something to do with it, but it kinda defeats the purpose when you have to alt out and disturb all of them regardless.