I'm not sure if Brennen.exe and Demon Rin argument / debating are already conclude as I'm only at page 15 before I decided to join this site. I just want to share some of my thought about this matter.
For once, Haki is not a technique. However, it can be apply into an object, or a body (basically any attack) that will later being seen as a technique. What I'm trying to say is, Haki doesn't originate to be a technique but once it was apply to something in particular, it can be sees as a technique. I understand why some people wants to look at it as a technique, but as I said, it can be apply, to becomes and be used as a technique. It's a spiritual or a personality traits things, and kind of hard to pinpoint the exact word for it when people are looking for something more physical.
I think I understand why people are debating about the choice of "Ambition" to be the word that describes Haki and whether Haki should be translated or not. I myself happen to comes from what Demon Rin referred as "Japanese fans" as in, I read from the original (and licensed) source whereas others read from scanlators material. Haki is a common word in Japan. Still, that doesn't mean every Japanese knows what it means or used it in regular conversation. It's more like there are nothing unusual about the word, it just like the way English speaker read the word "Ambition". We look at it as an ordinary word, but somehow, we are having a feeling the word actually have a deeper meaning to it. I also read other countries that licensed One Piece manga and they doesn't used the word "Haoushoku Haki". Instead, they translates the word into the country language. If the word was translated into English, it would be "Dominating aura" or "Conquering Aura". Note, this is coming from license product, which mean the translator is a professional translator and they also have a professional proof read in comparison to the online source most people have that comes from fans translating for others, and choose to translates everything in less professionally manner (I'm not attacking or degrading them just for the record).
This is probably the reason why the choice of word "Ambitions" seems confusing to the normal English speaker. Being ambitious simply means people wants to achieve something and this doesn't mean they want to achieve something positive, solid or visible to other eyes. The term can covered a lot of things. I don't really mind if the word Haki are not translated, but there should be some sort of translator note that will explain the meaning, and usage of the word. I think people are already getting used to referred it as Haki instead of reading it in a common way like most Japanese does so yeah, I guess it's alright to stick to it. The only thing it need is a definition or a translator note to avoid confusion.
I also think what Demon Rin is trying to point out about Luffy having the Ambition of King is due to the fact Luffy has the desire, or a strong will to becomes a King. Being a King pretty much describes that a person is going to dominate and conquer something in particular. Even though Luffy already makes a statements that he doesn't want to rules / conquer the sea, that doesn't detract from the fact that once he becomes a King, he will, have the image of conquering or dominating everyone that wants to becomes a King. I noticed there are some people on this thread arguing what is Rayleigh ambitions because they see him as nothing more than a retired old people that have no desire to achieved something in particular anymore. I think it is safe (even if it's not confirmed yet) to categorized Luffy's Haki as a "will to conquer". From there, we can theorized and categorized other sub type of Haki as well. I think we can categorized Shanks (or Rayleigh for that matter) Haki as a "will to protect" type. Now that we have the category, it's probably makes sense why Luffy's Haki is considered to be one of a kind (and probably the strongest type of Haki) considering the fact that a "will to conquer" can also have the element of "will to protect", and "will to be stronger".
Although this whole categorizing Haki are still in theory, one might argue that there are also a "will to kill" or "will to destroy". I just thought by having this category will at least makes people not generalizing everyone Haki in the same group. Everyone in One Piece has their own desire, goals, dreams and their own ambitions. It just depends on how strong their desire is. Those that have the strongest desire will project their desire more visible than others. Luffy has been shown to be really determined to be a Pirate King and not once, he has given up to achieved that title. There are others like Crocodile and Moria that wanted to be a Pirate King but obviously their will are not strong enough to becomes one as they are shown to given up on pursuing their dream / ambitions.