I'm looking forward to it. It looks like the casting was done well, the effects look good, and from what we;ve seen in the trailers, the sense of humor (humour, since it's British, after all?) seems to have survived the transition to film intact.
I think we'll hear a lot of uproar form the fan-base regarding changes to the plot, "not faithful enough to the books", etc. They've added in entire characters that didn't exist in the book (the freaky cult-leader torso-guy), and I'm sure they've cut a tremendous amount of stuff out. This doesn't bother me for two reasons:
1) The Hitchhiker's series has been adapted to a bunch of different media, and it's been changed every time. It was a different story in the radio show, a different story in the books, and a different story in the computer games. It will be similarly different in the movie, and as long as it's well done, this is OK
2) I've heard that the screenplay has been in the works for a long, long time, and that Douglas Adams had a lot of involvement. Many of the changes were his own suggestions.