The device I'm targeting is the HP "Enterprise iPAQ" which is a VGA device.
It seems that it always takes around 10ms to do the final "flip", that is, transfer the contents of the backbuffer to the actual screen.
I've tried CreateOffscreenDisplay + GDI BitBlt. And I've tried "FULLSCREEN" Display then Flip, and I can't get it any faster than 10ms.
Is that normal? Seems that with CreateOffscreenDisplay, if the backbuffer is GDI then GDI's BitBlt shouldn't take so long.