I use both OS X and Ubuntu. In comparison, Ubuntu is terribly slow, even on basic things such as dragging and resizing windows, let alone graphically-intense applications. This is both with ATI's proprietary drivers and the opensource radeon driver. Things are a bit better if I don't use a compositing window manager.
I am not sure who is to blame, X or the drivers. But most users won't care. They'll see that GNU/Linux has a bad desktop experience, and revert to whatever they were using.
I'm using Intel hardware on a large display, and of course Intel makes all the information available to driver writers and the X drivers are open source and very high quality. And there is no lag. I used to use Mac OS X before and there's no difference.
So this sample of two users seems to indicate that your problem is with drivers. Wayland will make no difference to your experience of Ubuntu.
I am not sure who is to blame, X or the drivers. But most users won't care. They'll see that GNU/Linux has a bad desktop experience, and revert to whatever they were using.