If you don't like Jim Carrey, don't go. He plays three major characters. Unfortunately, his Count Olaf character is his standard make-fun-of-everyone, over the top egotistical performance (think Ace Ventura). The other two characters are much more interesting to me. And if you are really interested in character development, check out the "making of a horrible actor" special track on the DVD.
Aside from that thought, I enjoyed the movie. There was a lot of dialog sprinkled with odd frantic bits of action - perfect for the bookworm child, but for the other 90% of the childhood population there is going to be disappointment at the lack of continual action/adrenaline. Violet (Emily Browning) is definitely a strong, well-spoken character, skillfully underplayed. The special effects are adequate-to-well done, depending on the scene. The big black snake (Horrible Venomous Viper) was a lot of fun to watch. The final scene when the kids walk into the house was really strong.