Meh. This type of bonus is basically what I expect most amiibo usage to be in any game, so it's fine. A fine addition if you happen to have a particular amiibo but you won't miss out on anything important if you don't. Everybody should be happy.
Personally I would have hoped for something more inspired than a Cave of Ordeals II if they were going to do a dungeon, but it's better than nothing I guess. Strange that Toon Link doesn't get you anything though...