The changes fall into three categories.
Good changes that flesh out the story and improve the characters- I.e. Aerith consoling Marlene or the Wall Market segment.
Changes that just pad out the game- I.e. Barrett walking through a tunnel.
Changes that are just wtf- Namely the ending.
I'd say the ratio is about 30, 60, 10 or somewhere around there. Most of the changes really didn't add much to the story, and were dull but inoffensive. A good amount of the changes really improved the game in a meaningful way. Then there were those changes that are best described as Kingdom Hearts bullshit.