Shambler: Of course the downside to using Flip False is that you will get tearing since the image onscreen is being redrawn at the same time the monitor is refreshing the picture. The reason for using Flip is to avoid this problem.
Rottbott: I've never found VSync to affect any of my framerates at ALL, except to cap them at 75...And I hate tearing.
I have a suspicion that mark uses the ONE_OR_IMMEDIATE flag when presenting the display, so that the game will still render synchronized with the vertical refresh unless the framerate drops -- at which point you may see tearing. Of course this would all be related to video card and drivers, so it may be that while one person sees no artifacts or abnomalities, another may, using the same code on different computers.