If you double the refresh speed to 120hz from a 60hz source, what winuae does is simply doubling the frame (or just wait till vertical retrace has finished) so in fact all frames got doubled. That makes the image judder, specially scrolls and sprites, fast moving objects.
Now it is possible to get cristal clear images without glasses on lightboost 120hz enabled monitors (as the one you have CFOU) due to this hack: http://www.blurbusters.com/zero-motion-blur/lightboost/
However, for the effect to be perfect you have to update the screen at 120hz, that is, your source must be 120hz. If you have 60hz source, and if you try to double the frame, you get the juddering/doubling effect (similar to blur but the same).
The solution: simple. Just add a black frame before each frame. You will have perfect clear, 2D animations like CRT. However, program must be modified to support this. There is no noticeable flicker at 120Hz as is fast enough to fool eyes, although maybe someone can notice it. The only thing noticeable is a decrease in brightness due to black frame being interleaved.
I have just modified MAME with that idea with excellent results. I have awesome, cristal clear with no blur, ghosting... in all arcades, like CRT.
I am asking for the same feature on the appropiate forum thread. Please support my petition