This movie is about impressing stunts. Period. That is all it is, and it does it well. Chan is amazingly skilled in both performing great stunts as well as coming up with ones you haven't seen before.
Great stunts also lay a solid foundation for action comedy. Many action scenes are really, really fun, mixing the stunts with fun situations. In particular, I found the car chase scene make me think "just when I thought there were no fun Bond-style chases left to make, Chan proves that there are". The only thing missing would be to play "The Ride of the Valkyries" at some appropriate times.
One more point in the favor of the movie is Chan's charm. He really has good screen presence.
So far, this is good. But let me mention what the movie does NOT have. It has no interesting plot to speak of. It has rather awful storytelling at times, moving from one scene to another with minimal or no motivation. There are even scenes with obvious remains from cut parts. Finally, the three female leads are all young, pretty and stupid. One "silly girl" would be fine but three of them? This makes them embarrassingly similar. It wouldn't hurt with one woman who were, for example, middle aged and with a professional attitude, or just not exactly the same personality as the others. I guess this is a cultural difference, in movies from the western world we are plagued with over-professional arrogant women instead, which is just as much cliché. Maybe we could get something in between, like an interesting character?
So, forget about the plot. Enjoy the stunts instead! They make me wonder one thing: How dangerous was this movie to make? How many times did Chan go to hospital?
10/10 for stunts. 8/10 for fun and action. 2/10 for story.
