Sounds interesting for sure! I can't really say how much I'll like it until I play the game, but for now, I really am liking the sound of it. The main reason achievements are so popular in 360 games is that they add an element of re-playability or extended playability to a game once you've completed the main storyline. I mean, I know Pokémon games usually have some sort of story post-game, but not that much (aside from GSC/HGSS, whose post-game was massive). I think it'll give you a reason to continue playing the game aside from trying to complete your dex.