The only things i can tell that are new are achievements,cloud saving,and a button you can press that will give you 9999/999 hp/mp,and a ton of gil,but you stay the same level.
WTF, you can play through FFVII easily enough as it is. It's by NO means a hard game.
I've got an original copy, and a copy from PSN, I don't really feel like playing it on PC.
If you're into it you can probably mod the game to get higher res textures and I think there's a mod that changes some of the cutscenes with cutscenes from Advent Children.. Also there are some hard-mods and yeah, a lot of stuff. Not sure if they'll work with this version of the game though.