Po discovers that there's no secret ingredient to greatness -- you just have to be yourself. This positive theme resonates throughout the film. The issue of eating as a coping mechanism is raised (Po has to learn self-control to break that habit). Additional themes include integrity, perseverance, and teamwork.
Not surprisingly, there's lots of martial arts action -- expect tons of high-flying clashes that include punches, kicks, falls, and more. That said, the fights are generally more thrilling than frightening, though they could upset kids 5 and under -- particularly the sequence in which villain Tai Lung breaks out of a maximum security prison.
Fairly clean, though the word "suck" is used prominently, and insults are hurled at Po by nearly everyone.
Lots of mentions of the fictional martial arts movies that the Furious Five and other kung fu masters were in. The movie also has many promotional tie-ins.