I think they're nifty. I don't really brag about them but they can be useful.
For example, Lost Odyssey gives you an achievement when everytime you learn every special ability that any character can learn. That what useful to know for how how I wanted to play the game, which was a lot of grinding the party members that I wanted to super high levels and learning the best moves from other characters.
In Dragon Age you get one for dealing a certain amount of damage in one hit. This useful because it let me know how high my damage can be and got me thinking about how to spec to get that.
I like when they clue you in to the upper boundaries of what's possible with the game. That makes them nifty to me, but not crucial. I rarely go out of my way to get achievements and I prefer the ones that you'd naturally get from taking your play to a higher level rather than just fumbling through the game. I would never play a game that I didn't enjoy just to get an achievement though. That ruins the whole point of even playing games imo.
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