Quoting Paranoid from 15:47, 12th Apr 2005
"the film also suffers by having an entirely nonsensical plot. It is driven by convenience and unexplained happenings" thats EXACTLY what the Hitch Hiker's trilogy was famous for! Adams gave the impression that there was a plot when really there wasnt (if you want proof just re-check the ending in mostly harmless!)
I also had that thought when I read the line about convenience and unexplained happenings. There aren't many better ways to describe the sudden rearrangement of deadly nuclear missiles homing in on your spacecraft into a whale and a bowl of petunias than 'convenient'. Although re your point about the end of mostly harmless - no, that is when it finally all makes sense, hence Ford laughing uncontrollably as he finally gets it. The great plot is revealled! But I didn't get it until I read the whole lot through for the nth time. Before that the last couple of books just didnt really fit. Personally, I don't think the series needed such a manufactured explanation as to why it all happened - I prefered the random sillyness, and the fact that the universe was out to get Arthur just because thats the way the universe is, instead of a great conspiracy.
Still, I await the film with interest. Most reviews / comments I have seen do not fill me with confidence, but even a poor HHGG film should be very funny.