Hello there! I found this thread by surprise and after reading people's thoughts I just wanted to say my two cents about all of this.
First of all I can understand why there are people who say that in the end this is just a typical and necessary shonen manga twist to go on with the history itself. But from my point of view there are two big differences in this case. The first one is that there are ways and WAYS when you do things, and I think that Oda has showed us since a long time ago that he has his own way of do what he does, and what makes it special is that it is unpredictable in a way that you like it because you'd never been able to imagine it before and in the same time it somehow manages to fit with the rest of the story in a "perfect way". The second one is because right now, there are in general lots of manga with very good histories, and of course within this group also includes lots of shonen manga (D.Gray-man, Naruto, FMA, Reborn! and Bleach one could say that they are the best known by general public) but not all of them can transmit emotions like One Piece do, and I think that most of the readers don't realize about this fact: that between doing a good job and get the reader thrilled (sorry I don't know if this is the correct word) there is a big difference that not every author is able to surpass, and Oda in this occasion has done it.
In reference to what is the scene that have impacted me the most I would say that it has been the succession of images of how luffy gradually collapses starting from the "waht are we meant to do now…?" until the final scene when he hits his head at the ground and says the final phrase which gives the name to the chapter; and of course the utterly defeated part, that although we know thanks to to the unspoken law of shonen that "the protagonist will always manage to go on", we have to have in mind that this is not the typical shonen manga on where the enemies are lineal and when you defeat one another will show up until the final fight and all the "defeats" in the course of the history had only been "little excuses" for the "necessary power-up". This is a tale about pirates who travel around the sea and are about to enter the the New World, where enemies can come from anywhere and probably all of them will be as strong as them if not stronger, and mugiwaras had to know for their own sake and also for the sake of the continuation of the history itself, that they have to be prepared for anything and anyone, not just for the "x obstacle which we have to defeat to achieve what we want".
By the way, and finishing my posting, I have to say that this chapter has reminded me of a recent chapter of HXH where Togashi, through Gon, makes an impressive work of how to show emotions that I have never seen in a manga in recent times (here is the link: http://www.onemanga.com/Hunter_X_Hunter/275/01/ ).
ps: sorry for my English and this long post. Bye!