Ambition has been a NAMED aspect of the series since 2007 when Shanks started making people faint in his presence, and Luffy has had signs of it since Sabondy in 2008, and Blackbeard revealed his nullification unique fruit around the same time. And in hindsight we realize that it was there on Skypeia in 2002., and Oda even had Blackbeard name drop it that far back, in an innocuous way… and it can be extrapolated Shanks used it in the first chapter, but I don't think Oda had it clearly in mind that far back.
Ambition has been in the series in differently named form as mantra for over 10 years, and its been named for 6 and a slowly built up Luffy ability for 5. Between knocking out the bull and his screaming at the execution platform took almost two years! Between his first signs of it and time-skip mastering of it (and he actually still has room to grow!) it was three years! Sanji and Zoro were only confirmed to have it a few weeks ago, without making a fuss about it at all post time-skip... five years after it was named. Why are people still complaining about it like its a new development that quickly came out of nowhere?
Yes, Oda recently added the shiny blackness to signify hardening. (And by recently I mean two years ago now after the time skip) Its fine, we needed some sort of visual cue rather than characters yelling out "is that ambition?" for the next 15 years every time it came up. How many times was it used in the war where it was totally unclear if anything was happening or not? It can still be invisible, and its just us as viewers getting the visual cue in, if that makes you feel better. Or you can say its a trained user being able to see it.
Its a GOOD thing more characters can do it now, it keeps it from being a broken inherited genetic trait thats unique to Luffy being the destined child. And yes, it means Logia are hittable now. Thats a good thing since, luck with Croc and Enel aside, every single logia in the series has been basically unstoppable. Can't just keep going "well maybe they'll find some mirrors to deflect admiral kizaru!" or "Maybe they can use the milky dial to trap Smoker!" because... that's dumb. It also at the same time explains why just having the broken devil fruit isn't enough to make you top of the world instantly.
I think the main problem is the tacky translation of raw "haki". If it was just left as Ambition like it was when Shanks first used it, it would seem more natural and an extension of the character's forceful personalities, (no one questioned it when Shanks did it, it was just a cool thing the forceful guy could do) rather than the random japanese magic power word that sticks out like a sore thumb.
@GiantGuy:
A character should be able to give a frightening look to show how serious and at the same time charismatic he is - fictional characters do that all the time, even in non-fantasy settings, so the effect would be cheapening to me if Shanks was just using a magical superpower and not radiating his own awesomeness.
…thats exactly what Ambition IS. Its entirely radiating awesomeness.