Achievements as a whole are great for World of Warcraft; they ask you to look at the game a bit differently, to create challenges for yourself, and to get involved with zones and stories that you might otherwise ignore. Unfortunately, they can also spur players and guilds to approach raid content in a way that's not necessarily fulfilling for all concerned.
Since Wrath of the Lich King, I've slowly gotten the sense that raiding as a whole is much less rewarding than it used to be, and this is a sentiment that's been echoed by a number of other players. Unfortunately, achievements -- originally intended to add another means of accomplishment to raids -- may well be among the causes.
EDIT: This article resulted in a lot of discussion, and the subject was revisited two weeks later. You'll find it here, at OverAchiever: Reconsidering achievements and raids.