Some good points here about Disney's "Let It Go" from Frozen. A few minor points I'll add:
-I'd argue that Frozen is a well-written song, save for its title. Disney's songwriters have always achieved popularity in their compositions by entitling their songs with common catchphrases (e.g. "Be Our Guest," "Mother Knows Best"), and "Let It Go," while a common phrase, has difficulty fitting in with the rest of the song's lyrics. To "let something go" usually involves sacrifice and the severing of an emotional attachment, whereas the song is about the opposite.
-I should point out that "Let It Go" is performed, in the movie, by the light and laser-like pipes of Idina Menzel, who also most famously portrayed Elphaba, the "wicked" witch of Wicked, who again discovers her dangerous potential and needs to relocate and build a kingdom. Elphaba's likely most popular song from Wicked, "Defying Gravity," has some very similar (and stronger) rebellious themes to "Let It Go," and it's not nearly as seen (if at all) as "Let It Go" to fly into the face of the Wicked's message.
-I would be surprised if "Let It Go" upset U2's "Ordinary Love" for the Academy Award for Best Original Song that's going to be handed out a week from Sunday. I've always respected Disney's creativity and execution, and it's good to see some fresh blood in Frozen's music department. But they're not U2. And Elsa is not a real person.