I haven't read the comics or seen the shows so I don't know if the film was a good adaptation. But as a stand alone film I thought it was very good. The film is kind of a mix between Iron Man and the Dark Knight. Although there is a strong comedic element to the film there are a fair amount of action moments (Especially towards the end). Kato was probably the best character in the film. He does nearly all of the fighting in the fight scenes and Jay Chou does a good job in them. Seth Rogen plays a pretty good Green Hornet and Christopher Waltz plays a great villain.
The Black Beauty looks amazing in the film. Chudnofsky is a great villain. The overall plot is pretty good and the special effects are good. And the jokes were hilarious 90% of the time.
Cameron Diaz's role is a bit pointless and sometimes the jokes in the film felt a bit out of place.
Great film, really funny and action packed. A must see!