I also have Nvidia on my laptop. Doing some testing it seems that I always have sync rate problems running full screen (not always visible). From what I understand of the help, it sets the sync rate to the same as the screen's refresh rate. But what happens if there are variations to the framerate? Printing the frame rate setvsync( 1 ) does the same as setsyncrate( 60, 1 ). I get about 59.4 FPS. Not a solid 60. So I have a line going through the screen (moving from top to bottom) where the top is one frame and the bottom is another.
The normal definition of vsync is that the game renders the frame and then wait for the screen to refresh, before rendering another. This is not how AppGameKit handles it and that's the problem.