For me it was the lost potential. I liked those characters, I liked the universe they inhabited, I liked the originality of the concept, and I was curious about some of the plot threads being set up. Then POOF! All gone.
And a lot of the anger rises from Fox having done exactly the same damn thing over and over in the past:
Space: Above and Beyond
The Adventures of Brisco County Jr.
The Lone Gumen
Kindred: The Embraced
Greg the Bunny
It continues to confuse me why Fox would even order a genre program any more, or why a producer would want Fox to buy his show.