I'm strongly divided in my own mind about this movie.
The half of me that loves the Hitchhiker's series hates this movie. Just not a good adaptation at all. The only thing they did right was thier choice of Martin Freeman as Arthur. I'll never read or listen to the book without seeing his long suffering face in my eye.
However, if you step away from the expectation of the source material, this is actually a fun, weird movie that is quite entertaining.