You'll probably recognize me if you spend much time on that server. But anyway.
Killhouse is a dreadful map, it's just not possible to sit on the hq for long enough to capture it... and even if you do manage it, expect a hail of grenades and LMG fire to cut you down within a few seconds.
I don't like creek either, it's just too open. That waterfall hq is impossibly difficult to capture and the one in the cave makes me rage like little else.
I think Bloc is OK, the buildings do provide ample cover. You can camp in a building if you want but eventually the screwy HQ spawns are going to stick an enemy right up your jacksie.
countdown and bog both have one horrid hq (center for countdown, container for bog) but i don't think they're bad enough to say that they need to be removed. cod4 doesn't have many maps and if these 2 were removed then we're not left with a very big rotation.
there's absolutely nothing wrong with downpour imo (am i the only person who likes that map?), and if pipeline was removed i'd probably break something.
wetwork is a fail of a map, wouldn't miss this one at all. probably wouldn't miss showdown either but i can survive with it there. actually, i really really wouldn't miss showdown. dodgey map