Agree. It's a character introduction film, so it really can't be as much fun as a film with established characters.
The fights were pretty awesome, but they lost me with the final fight. It was fine, but a bit too much magic monster battle in a film about kung fu fighting.
The overall story was pretty solid with a very good main villain. (I consider the one throughout the film to be the "main" villain.)
The humor was 50/50 hit/miss. Asian Kat Dennings (tell me she doesn't look, sound, talk, and act just like her) did a good job, but I did NOT love her role in the final battle. Sometimes ancillary characters need to stay in the background. Ben Kingsley seemed to be there as an apology for how they ruined him in Iron Man 3. He was funny, but lame at the same time. Do we really need two funny sidekicks in the same movie? I don't think it really worked here. Kingsley could have been an extended post or mid credits scene and it would have been perfect.