I agree with Previous in the sense that games were cooler when you got stuff for doing bonuses. Like in Link's Awakening DX you'd get a new shirt for completing the Colour Dungeon, or in The Minish Cap Kinstone fusions actually made you want to do them because you always got something.
That said, I don't dislike achievements that much. Sure, they're not as good as the above, but if the game doesn't have them anyway there's no harm. As far as I'm concerned achievements add replayability, especially with initially shallow games. For example in Renegade Ops, there are optional missions that you might not complete. However on Steam each optional mission has an achievement for completing it, which personally gives me more reason to go back and try to complete it.
I can see Diogalesu's logic, but well thought up achievements should cover that. Either you make achievements for all the extras, or only make a few for the extremely difficult/unique ones. If the former, you'll try to get them all, and if the latter, you'll probably discover the little extras by yourself and know that the achievements don't include all the game's extras.
That said, I don't dislike achievements that much. Sure, they're not as good as the above, but if the game doesn't have them anyway there's no harm. As far as I'm concerned achievements add replayability, especially with initially shallow games. For example in Renegade Ops, there are optional missions that you might not complete. However on Steam each optional mission has an achievement for completing it, which personally gives me more reason to go back and try to complete it.
I can see Diogalesu's logic, but well thought up achievements should cover that. Either you make achievements for all the extras, or only make a few for the extremely difficult/unique ones. If the former, you'll try to get them all, and if the latter, you'll probably discover the little extras by yourself and know that the achievements don't include all the game's extras.