it would be a commercial disaster if the game can only be run with dual video card. i can run it near maxout graphic with a 7900gt 25fps in the forest.
i thought oblivion was a hog and then i played gothic 3, if my $300 card cant handle it at decent speed, forget it, i'm not playing.
to improve fps, i recommend the grass mod for oblivion, i think the original patch of grass has 24 blades, in a grass field thats thousands of objects, the mod reduces it to 8 blades and still looking good. it also shorten the grass height, this is something very annoying about oblivion, the grass taller than your head.
i dont even consider myself rpg fan, rpg player here and there. but i followed morrowind lore closely and it remains one of the best and most intricate story. to me oblivion story and theme is just a rip off of lord of the rings movie. a lot of times i saw things coming. except for the paradise, which was well done.
there are things you will experience not offered in morrowind though, is the fighting gameplay, as an archer. its almost like a sneak fps. i have a mod that allows me to hide from enemy. when i first started playing the game (2nd time through) i found this flooded cave full of naked argonians and water tunnels. it was one of the best experience, almost Deus Ex like, i have no water potion or spell, and i have many near death experience and having to evade the argonians and doing hit and run tactics. being able to hit a deer from a thousand feet away from ontop a hill is also very satisfying. usually though, enemy just charge toward you and attack mindlessly, as your level goes higher, they starts blocking and strafing.
i think the battle mechanic is the largest improvement from morrowind to oblivion. more traditional rpg'er might not like it, but for a fps'er like me its very good, very seemless.
i also installed a mod that add unarmor skill, as the developer did not add that skill for this game.