Tobold recently made a blog entry about the waning influence of the "hardcore" player in WoW. I find myself moving back and forth about his opinions on the game, but this point I agree with. And, the people who feel that WoW has changed, or gone soft, probably are the people who need to move on. Given the choice between millions of people leaving because the game is too hard or having less than a million people leave because it's too easy, I know where Blizzard will go. That's a lot of money to give up to remain the "hardcore" king of MMOs.
Even if you think that most of the more casual players only play WoW because of the percieved uber-leetness of the raiding, that bar has moved. Now more people will be in the raiding dungeons, killing bosses, instead of reading about hardcore raiding guilds doing it and hoping they could one day make the cut and be in there, also. That will surely keep people playing longer, and consuming more content.
While I'm not really happy about the achievement system, it does provide a way to give the serious raiders challenges beyond just clearing a raid instance. It's not the same as having been in a small group of people to even see the inside of Black Temple, for example, but even the most accomplished Diablo II player didn't see any content I didn't see. They just beat the game on a much more difficult level than I had the time or skill to do. Hooray for both of us.
I welcome our new, kindler, gentler World of Warcraft.