i haven't had any REAL trouble with story bosses...Ultimicia was a bit of a stubborn b*tch...especially when she summons that thing once you get her health low enough

otherwise, pretty much what everybody else has been saying, Omega weapon from 8 and Ruby weapon from 7 (i found Emerald weapon quite easy, it just took a long time to kill him [which isn't a problem if you have the Underwater materia], but in saying that i kind of cheated...i had a master phoenix summon paired with a master 'final attack' materia, so everytime cloud died, he would summon phoenix and revive my whole party [cos he was usually the last person to die]...then i had Knights of Round [used with W-summon] on cloud and mimic on the others, so i'd do a double cast of mastered KoR, then mimic it with the other two, which is 6 KoR every turn...and even doing that took ages to kill him)

also, although i beat a fair few dark aeons in FFX, i didnt beat them all, and i imagine penance (i think that's its name) would have been quite a challange...anybody to comment on this?