I love this game... I really need to set some time to play through it. I remember playing through it when I was a lot younger and I loved it almost as much as FFVII, but I think the fact that there were so many endings made it feel like an incomplete experience. But still, amazing!
The endings aren't too important. They only matter when it comes to the final boss of one of the post-game dungeons (Urssa Cave Temple). If you get Fayt's solo ending then you have to fight Fayt and Luther, but if you get an ending with another character then you have to fight Fayt and that character. It's definitely not worth it to get Nel's ending, though. Fayt/Nel is the only combo that I have more problems with than Fayt/Luther. Everybody else is really easy.