
Sometimes.  It depends on your monitor and your timing.  If you don't
have enough vertical front porch and you use XOR composite sync you can
get even/odd tearing at the top of the screen, which is very sensitive
to the HHOLD control.  It looks like what you would expect if you
scanned the even fields (say) onto a sheet of mylar and had pinched the
upper left corner with your fingers and started to tear it off the tube. 
With proper composite sync (equalizing pulses) the interlace is rock
solid. 
