I have beaten it a few times. I don't remember exactly what I did, I'll have to go back to one of the old saved games and see what I played. I've been mostly playing the maps against two or three AI opponents. Quite a challenge. The computer is enamored of a massive early rush - usually 12 Zealots or a nasty combination of zerglings, hydrolisks, and lurkers. The only good thing is that when the computer is playing Terran, it's fairly easy to beat (no idea why) the rush.
I love ghosts as well. When four maxed ghosts can take out 12 battlecruisers (using lockdown, and then having some anti-air unit take out the frozen cruisers), you know you have a key unit.