I felt like they kinda petered-off toward the end... like Adams was tired of writing them. I especially didn't like the ending. (Dent dies and the universe unravels, because the Vogons, of all people, want it to?)
I prefer to end with the death of Marvin the paranoid android (after reading God's last message to all of creation), or the book after that one.
The last book left a bad taste in my mouth.
-kv