Not being a big Seth Rogen fan, I went in with low expectations. I was more into seeing this variation of the Green Hornet and Chou's version of Kato. Christopher Waltz was also big on my list of why I saw this movie.
The editing was choppy and the storyline didn't have a smooth flow. This was more surprising than annoying (again, my expectations were already low) as I was still able to keep up with where things were going. The fight scenes were good, the banter between Green Hornet and Kato was entertaining, the subtle Bruce Lee references were cool.
Seth Rogen was mildly funny, Christopher Waltz' talents were underutilized, Cameron Diaz' character was pointless, Jay Chou stole the show.
Overall, this was not a horrible movie, mostly light matinee entertainment. However, if you're expecting comicbook hero story-telling caliber like Tim Burton's Batman film series, you'll be disappointed.
See the movie if you are a Seth Rogen fan. See the movie for Jay Chou; he admits he's no Bruce Lee, but he did justice to the character and saved the movie.