I hooked a Hercules card and monitor up to my 486 with Linux and tinkered around. It was kind of cool to be able to draw graphics on a second amber (or was it green) monitor, but I never could get 2 terminals to work. Just writing directly in Hercules memory from root.

If I recall correctly, one could also debug a DOS programs and print stuff on the Hercules while doing graphical or text UI on the regular VGA.