orcishgamer: Achievements are just another form of feedback a game gives you. Denigrating them by calling the "dog biscuits" isn't very self aware. Now, like any gaming feedback they will be both poorly done and masterfully done, but that's not a flaw inherent to them in particular.
Regardless to whether one believes them poorly or well implemented, they do call to the same intoxicating feeling of progression and improvement that gives some people the "just one more turn" feeling, and any kind of levelling system - they are, in effect, dog biscuits - a boon that you've progressed a little bit or done something good enough.
Some people are more prone than others to be intoxicated, and some people require different kinds of biscuits than others to get the same feeling, but they are really the same thing.
Note, I'm not calling them good or bad (at least trying not to), but I'm trying to call them for what they are.