I agree. I mean, I don't think anyone expected Luffy to develop Gear 2nd and 3rd during the Enies Lobby arc. Sure, people probably expected a powerup, but that was his first powerup, then came his release of CoC, which at the time really wasn't something that benefited him, it just happened at some opportune moments.
As for Luffy eating Ace's DF, I don't mind at all. All it does is make him immune to punches without Haki, and adds some extra power to his punches. As it seems right now, he has developed it to its full potential. That probably isn't the case though. But I think Oda dealt with the problem of Luffy eating Ace's DF when Luffy said that he knew that you can't have two DFs at the same time. In other words, it doesn't seem that he will accidentally eat it.