Both versions share...
THE THEME SONG! I got chills in the theater when the title music of the TV series blasted on. That was great. There's a cool cover of the theme song here:
http://www.myspace.com/alonzoreason
I think both the series and the film compliment each other well. I love how the series goes into more of the random side notes like the book, but I like the film more as a cinematic experience. I also wish the series had more name actors involved. Where was the Monty Python crew on this? John Cleese would have been a perfect Slartibartfast!