I saw the TV show a long time ago (it was taped obviously as it was on in the early 80's I think) and liked that alot. I thought the movie was pretty cool but some of the characters were just wrong compaired to the TV show (which was very accurate). Marvin especially, he looked totally different and more cubic in the TV show, there's actually a 2 second glimpse of the origional Marvin in one scence of the movie, can't remember darn it. I liked the vogon costumes, those guys looked so stupid, it was awesome.
Yeah, you really have to have been previoulsy exposed to the series in some way to enjoy the movie Fred, there's a lot of stuff I would never have gotten otherwise. Some guy in the movies with me didn't have a clue what was going on, he saw the dolphin in the beginning and asked what movie he was watching, then if it was a preview for flipper 2, then he just got up and left.
You also can't take the special effects seriously, it sort of goes with the wackiness and randomosity of the book, I guess it's meant to look sort of cheap and awkward.
Well that's my 2 pennies anyway.