Vertical synchronization would REALLY improve the experience.. The tearing is awful especially in scrolling games and demos (which are smooth on real hardware).
I tried forcing vsync with drivers in OpenGL with some success - 320x200 (13h) seemed to work well, but mode-x was really buggy and slow, so it apparently needs some fixing.
However, this happens only in fullscreen! When Dosbox runs in window, everything's fine - no tearing and no slowdowns. (I was testing this in Win7+Aero and ATI)
Why isn't vsync enabled by default? it's a pretty common feature in emulators