Achievements are irrelevant to me, unless they provide some tangible in-game rewards (like in the first Mass Effect: do this thing, and you'll get a permanent boost to your max. health - this kind of thing). I simply don't see the point in bothering with them if they do not.
So there is the answer to the question: achievements are a good thing if they reward you for doing them. Otherwise they are just padding, a cheap way of expanding game content with minimal effort.
So there is the answer to the question: achievements are a good thing if they reward you for doing them. Otherwise they are just padding, a cheap way of expanding game content with minimal effort.