I saw Hitchiker's Guide to the Galaxy recently. I thought it was really good. I'm sure it didn't quite follow the book, but as it was so long since I read the book I couldn't tell all of the bits that were new. Pure fans probably hate it, but I'd recommend it to half-hearted fans. It's quite quirky, so I wouldn't recommend it to people without a strange sense of humour.
I was very restrained and didn't recite all the famous lines as they came up, apart from at one point. The old TV Marvin makes a cameo appearance which was a nice touch.