This is one character where it actually makes a lot of sense to do a race switch from the original. Casting an Asian guy to play Iron Fist seems far less offensive to the source material than say a black Heimdall or a black Johnny Storm. I am FAR from a whiny liberal and I certainly don't believe in shoving diversity down people's throats, but I've always thought it was a little silly to have a white guy as Marvel's greatest martial artist.
Mind you, I have never and will never read an Iron Fist comic book, so I have no attachment to the character whatsoever. I can see how fans of his may wet their beds over changing his race; hell, I was pissed when X-Men came out and they cast a 6'2 Aussie to play Wolverine.
Many of the reviews I've read have said that the fight scenes are bad and the guy they cast is shitty at play fighting. They should have cast Daniel Wu, that guy can tear up a choreographed fight scene (I just started watching Into the Badlands, he is amazing!)