"The End" rocks! I've gotten it a few times - it takes forever on Selphie's slot but if you keep at it it works. Basically, wings come down and fly the enemy right out of battle and you automatically win. However, I've never tried it on Ultima because its only supposed to work on random encounters, not bosses, and I've always considered Ultima to be a boss fight. It's worth a shot I suppose.

As for me, I make sure my characters have "revive" and "recover." A couple of Phoenix Pinions don't hurt either. If anyone has the auto-haste or auto-protect, that's nice too. Aura is your friend - keep Squall using his limit break. Summon Cerebrus so that everyone has triple. Summon Doomtrain and cast meltdown to limit its defences. Cast haste and do your best.