Though it still had some comedy in it, this is the most serious Jackie Chan film I've seen. But then, I haven't really seen that many Jackie Chan films, so... Anyway, the action scenes, and comedy scenes were just right. The only thing I didn't find all that pleasing was the romance part--and I guess that's weird, coming from me, as those are the parts I normally like in movies. But Jackie Chan having a leading lady just seemed wrong. I mean, the cute guy in the movie was most definitely his sidekick, Frank, played by Nicholas Tse, so why wasn't he the one with the love story and Jackie Chan can just have family issues, like all the other older cops in the movies?
I guess that would be a little too cliche, and considering Nicholas Tse doesn't really need to play a romantic guy for every girl in the audience to fall in love with him anyway, the film makers decided to let the "old" guy have the love interest.
Nice background story on Frank, by the way. Way to go, emphasizing the relevance of a character's wardrobe. And the bit that's related to the X-Games was just fantastic.
Recommend you to see this movie if you want to see an action film that's got everything you want--explosions, martial arts, car chase, cool stunts, laugh-out-loud moments, and a pretty good story line too.