Big question: Did it strip during installation or removal? And was there Loctite? An unlocked screw that stripped during installation is MUCH easier to extract than a locked one that stripped when you tried to remove it.
EDM works slick if you know a guy with access to one.
Failing that, buy a set of really tiny little carbide burrs from Lee Valley and patiently carve the screw out.
I've never had success with a twist drill or the patent easy outs, but others with more skill may.
Lemme see if I can dig up pics of having done this before...