His maturity level is so inconsistent from episode to episode that, you'd almost think he had multiple personalities.
Todays episode (the first half) is a case, of the more mature Luffy, who has enough attitude and decision making initiative to make you belive that he can become king of the pirates, and then the next time you see him, he will be bouncing up and down on a suspension bridge like a five year old in an inflatable castle.
That's not to say, that it's wrong to give him a bit of whimsy in his personaity, but it's gotten to the point where I think his whimsy needs to be a bit more age appropriate for the story to word, cause the fanbase is aging, and I think more fans will start to feel juggled each passing year.
Which Luffy do you prefer? the cadidate for pirate king, or a kid who is meant to be laughed at?