I hate fast zombies, but in a good way. I never really considered slow zombies all that threatening unless you back yourself into a corner like an idiot and there's a bajillion of them crowding around you. I hate fast zombies in that they are more terrorifying, which is why the developers designed the zombies like this in the first place. It's a good way to make players panic and such.
However, I can foresee growing weary of them if everyone and their mom starts making games with quick-moving zombies. It seems like if one person makes something inspired by a multitude of sources in other media and it turns out great, everyone blindly rips off that thing without actually seeing its sources. Star Wars is a good example, where they were inspired by westerns, adventure movies, and other sources, and then studios started ripping off Star Wars.
So, I can picture everyone getting tired of fast zombies when other studios start riding off of the successes of Left 4 Dead and Killing Floor and making zombie games with fast zombies.
Internet Kraken said:
A real zombie can't run. Rotting flesh doesn't move that fast!
Well, the fast zombies in games and movies are nearly ALWAYS not actual zombies. The zombies in 28 Days Later, I Am Legend, and Left 4 Dead are all living organisms that were mutated by a virus, not reanimated dead corpses.