I'm more or less happy with what they did with the plot - a bit of a shame that a couple of the best jokes weren't used, but I suppose it's a bit difficult to get everything into a film that length. The Arthur / Trillian ship doesn't quite work, but it's not nearly as bad as I'd been led to believe by some other reports of the film. There are some nice touches, such as the Vogon homeworld, the poetry-reading scene, and a quick glimpse of the BBC version of Marvin, and the Magrathean shop floor scene is everything I'd imagined.
One thing you should definitely watch out for - towards the end of the closing titles there's a guide entry bit which a lot of people missed because they left the cinema early.
I came out humming the "so long and thanks for all the fish" song, but a couple of hours and it's gone from my head completely. Weird.
Am I a terrible person for admitting that the first thing I did when I got home was put the commemorative booklet and my ticket on sale on eBay? Probably, but if I keep them they'll just gather dust.
Here's some photos of the booklet - can't scan it since I don't want to damage it: