I liked Marvin's voice, though his costume was good, it was a little jarring to my mind. I did like the fact that the TV series Marvin had a cameo in the 'queue scene'. As for the rest, fairly good although the love story is cheesy. I thought the Vogons were the best Vogons, total bureaucrats! And Bill Bailey was the best whale ever.
Zaphod wasn't a selfish megalomaniac. He was a selfish psychopath instead. The head thing was only slightly annoying compared with that.