from the opening shots of the playful cetaceans and the catchy tune:
"So long and thanks for all the fish"
they got it right. Not that there are some modifications to the original narrative, but it works really well. There could have been more bits from the guide itself, and the fact that Ford was a field researcher for the book could have been expounded on more, a really fine adaptation and give it a thumbs up. The conclusion was a perfect set up for restaurant at the end of universe. Some of may fave bits were missing, but many were there, intact and perfect: think sperm whale and a bowl of petunias. There are some easter eggs there, in one scene, IIRC, the BBC Marvin is present as an "extra". Speaking of Marvin, Alan Rickman does a great job of bringing the right about of "programed pathos" to the voice, even if it sounds like Professer Snape. I probably will go again, I liked it so well, take someone who has never read the book and get thier response.
What I really missed is some of the verbatum wit present in the novels, there were many intact in the movie, but other scenes were "rewritten" for the economy of the big screen and loose some of the sparkle present in the original. But there are other bits of detailed included like the Vogan "chairs and jeweled crabs" for da FANS that really made smile broadly. The SFX are pretty smooth, the construction floor of magrethea is particularly impressive. I thought to myself, this is close to Ringworld scale stuffs and shivers went down my back as I thought of potential of Ringworld movie SFX..then had to force myself back into the orgy of eye candy as Arthur and Slartibartfast tours the construction floor.