There was no point in having her stay a unicorn. She was no longer the last of the unicorns, so she could be with her true love and not have her species become extinct. Plus, when she was human she finally felt emotions and was her happiest when she was with him. It really seemed pointless to make her a unicorn again.

I think the ending is very fitting, even if it's sad.

It illustrates why unicorns can't afford to feel things like compassion, regret, and love. In the beginning, it's easy for us mortals to scorn the unicorn for being selfish, aloof, and uncaring. The problem is she will live FOREVER. We can afford to feel love and thus heart-break because we don't have to feel it very long. They'll carry that sorrow with them till the end of time; and it's perfectly illustrated by the unicorn who starts off aloof and uncaring but learns to feel regret and love, and will have to live with it forever.

Plus, there's a beautiful, tragic irony that she succeeds in saving her people but at the cost of her identity as one of them. That ironically she's even more alone when the world is full of unicorns than when she was the last of her kind, because she's emotionally separated from them from having learned love and loss.

But if she stayed human, wouldn't she die and not have to live forever with that sorrow? Plus, she'd be with the one she loved, so she wouldn't have to feel sorrow anymore? It seems very stupid to have her choose to be miserable and basically have learned nothing from her journey and experience. Wouldn't it be a better lesson to teach people that living forever isn't important if you're alone and can't get close to some one, when you should really feel something for other people, be happy, and embarrass it because a living creature is supposed to feel love and have someone in their life? I always found the ending to be really stupid. I even met someone who loves sad endings but she thought that the ending to this movie was stupid. It really makes no sense. It seems to just send a message that if you love and feel for another, SCREW IT! Just be alone and feel nothing, even though you have the option of being happy.

I agree with Tygers' Come on, Katara, let it go.

The movie has a strong message, and I like that it goes against the typical Disney ending of "and the girl left her world/people/identity to be with the dumb prince" like the Little Mermaid and Anastasia.