The best thing about achievements are that they teach you new ways to play a game (IMO). When I play a game with well-designed achievements, I'm constantly learning: "Oh, I can approach enemies this way." Or they make me try a new weapon type: "Oh, this weapon is effective in this situation, now I will update my default play-style." I would love to have such achievements for Emacs, because I feel like I don't use it to its potential, but I also don't have a good sense of directions to explore.