This show should have worked - it had all the right points. Star power voices, great characters, and snappy writing.
The series featured great stories, constantly challenging the viewer to laugh at things that other series wouldn't touch. An evil Santa? The severed head of Richard Nixon? Brilliant! The voices featured were all great (although Fry always just made me think of Stimpy...). They really brought the characters to life.
The characters themselves were very sharply imagined, and worked well off each other. Stories tended to be organic in nature and the humor developed from the characters, rather than just the situations (A very Simpson-esquire idea).
In short, this was great. Watch it on Adult Swim, and buy the DVD's. 9 out of 10.