I didn't go into the film expecting much. Indeed, the first review I saw, at Planet Magrathea, is an extended spoileriffic rant that completely savages the film. But since then I saw and heard a lot of reviews that were all over the map -- none that really loved the film, but a fair number that liked it mixed in with the pans. Unfortunately, I found that it mostly lived down to the negative reviews.
First, the bad. The script was the greatest disappointment. It wasn't uniformly bad -- it really couldn't be, given how good the source material was. But it was surprisingly weak.
I've heard many comments of "but Douglas Adams wrote the script, so this must be what he wanted!". It's unconvincing. I simply don't believe that he had final script approval, because so many of the jokes are broken. The fan of the story will recognize many of the setups, but the punchlines are missing. From the cellar joke to the Vogon poetry, it's as if the writer just didn't get the jokes, so they cut the punchlines for time. That's the real tragedy of the movie. As the Magrathean review points out, witty dialogue was always Adams' strength, so getting that wrong really does the story a disservice. There were perhaps a half-dozen lines in the movie that took me by surprise, leaving me sure that they were new dialogue from Adams. The rest just didn't sound like him.
(And frankly, even if Adams *did* write this script, it doesn't change the basic fact: this is by far the weakest of the versions of the story. Bad is bad.)
The casting and acting was uneven. In some cases (which I'll talk about later), I thought it worked reasonably well. But several choices were just odd. In particular, Ford and Zaphod were changed from the expected, and not for the better. Instead of his usual right-angles-to-reality oddness, Ford just comes across as goofy. And Zaphod gets a makeover as a sort of rock star with (as msmemory put it) Bob Eggleston Hair. That's not a wholly crazy idea, but in practice his ego gets played so far over the top that he comes across as irritating rather than strangely cool. And while John Malkovich is always brilliant, he is given nothing to work with here -- his entire segment could have been excised from the movie for the better.
The direction is just plain terrible. Throughout, I had a feeling that at least some of these actors could have done a good job if they'd been directed properly. But again, the movie commits a mortal sin: it has no comic timing whatsoever. Even when they leave the jokes intact, the delivery falls flat. This is good material -- the radio show was deadly funny, IMO. But there were scarcely any chuckles in the audience when we saw the movie.
Finally, the cinematography was again uneven. Some bits really clicked -- in particular, the Slartibartfast sequences are great. But a number of sequences were apparently shot with hand-held cams to give them that modern edgy look, and it simply distracted. Indeed, between that sense of odd unease and the peculiar surrealism of much of the movie, they seemed to be less influenced by previous HHGttG versions, and more by Time Bandits. Which is a fine movie, but the juxtaposition of styles was strange.
Okay -- all that said, the movie didn't totally suck. What worked?
Some of the actors clicked nicely. While I don't think that he was good as Simon Jones in the original, Martin Freeman acquitted himself reasonably well, getting across the sincere but slightly clueless Arthur Dent properly. Zooey Deschanel's Trillian was one of the few good tweaks to the story. Trillian has tended to be pretty ancillary in previous versions, but here she's front and center, resembling (as msmemory pointed out) Marion Ravenwood in a number of respects. If she'd been given better dialogue, I think she would have been great. Alan Rickman is utterly perfect as the voice of Marvin, and Stephen Fry was born to be the voice of the Book.
Speaking of which: the Book is the one element of the movie that consistently shines. Perhaps not surprisingly, it's also the element that changed the least from previous versions. The graphic style goes well with the text, they (mostly) get the jokes right, and the droll humor manages to come through.
The special effects are mostly excellent, as you would expect of a modern big-budget film. They are pretty, but with a very subtle edge of cheapness that works very well with the material. As previously mentioned, Slartibartfast gets the best scene in the movie, segueing from a segment that is downright BBCesque in its dowdiness to one that is so strangely magnificent that it deserves to be considered the definitive version of the New Earth scene. It was the one part of the movie that I thought was a proper homage and enhancement of the material, rather than simply screwing with it for the worse.
Finally, there were elements that others have complained about that I didn't mind so much. The rework of Marvin's look didn't bug me (and I was amused to see the original Marvin lurking in the background of one scene). The emphasis on transformation in the Heart of Gold effect was stronger than in the original, but wasn't entirely an invention, and largely worked for me. Finally, I didn't mind the largely-invented romance plot, which becomes a major element of the movie -- I didn't think it quite worked, but again I think it would have done so in the hands of a more competent director.
Summary: Really, the tragedy here is lost opportunity. After 20+ years of people talking about making this movie, it's really sad to see a version that is just weak like this. It's not horrifically awful -- it's just nowhere near as good as it could have been if the people making the film had understood it better. Viewed both as a work on its own, and as a version of Hitchhiker's, I wind up giving this film a C-: Thoroughly Mediocre. There are good bits, and I didn't come out wanting my two hours back, but there's just no reason to bother. Go get a copy of the TV series instead -- the effects aren't as good, but the script is ten times better...