What makes Merida interesting is not only is Pixar *finally* creating a film with a female protagonist, but from what I can tell from the trailers she has no love interest - making this the first Disney film to feature a princess character whose happily ever after for the moment doesn't involve finding a man. Feminists rejoice!
I have to say, though, that while I consider myself feminist and am very excited to see Pixar's Brave, I do not have a problem with the romantic love stories of the other princesses. I love a good love story. What bugs me about some feminists is that they act as if woman shouldn't be feminine at all- as if it is a sign of weakness to be girly and romantic. The truth is while a Disney princess usually end up with a man on her arms, that is not always the entire goal of the character. I'll grant that Snow White seems to have very few goals beyond being swept away from her grim reality by a handsome prince and Princess Aurora has very little to do in her story, but Cinderella's desire to go to the ball had more to do with wanting to seek out joy and escape her stepfamily for a night than specifically to fall in love. She doesn't go expecting to dance with the prince- she just falls into it.
Ariel is the first Disney princess to have real spunk and spirit enough to put changing her life into her own hands. On the surface, it might look as if she sacrifices her whole world just to be with Prince Eric, but really it was an extension of wanting to be part of the human world.
One of my biggest pet peeves regarding the princesses are people who claim Belle has Stockholm Syndrome- the idea that Belle is acting like an abused wife who refuses to leave. Belle sacrificed herself to save her father, and when she felt truly threatened, she did leave. She only returned to the castle because the Beast saved her life! She never sought out to change him. She only helped him along when he showed her with his actions that he wanted to change. She didn't love him until after this point.
The most recent additions to the Disney Princess line are the very different Princess Tiana and Rapunzel. Tiana has amazing drive and passion with a dream to open her own restaurant. Rapunzel wants to see the world outside her tower. Both meet their loves by chance while aiming for the path to their dreams.
I'm proud to be a fan of the Disney princesses- I have no shame in it. I spent four years working at Cinderella castle completely immersed in their stories and little girls in sparkly dresses. And while the princess franchise turns me off when it generalizes the characters and makes them all about tea parties and pretty hairdos, when one sits down and appreciates them as individuals, the beauty of their stories really shine. If I have daughters someday, they will be allowed to play princess and be as frilly and pink and girly as they wish. It won't make them into weak women. And if they decide they don't want anything to do with that stuff, that's fine too.