I've only seen the first episode. Overall my opinion is, while I can see where some of the criticisms are coming from it's not near as bad as I expected from the reviews. I had low expectations going in, this was never a character from the comics that I knew much about or read much about. I'll leave it to others to determine how faithful this is to the comics, because I have no idea. The most I knew of Iron Fist was from some of the Marvel based games, like Ultimate Alliance.
Again I've only seen the first episode, so I'm trying to not be harsh about some elements that i thought were not explained well as I'm assuming they'll be explained later on. The story telling in this, I think is somewhat weak, but I do like the actors, and they did a reasonably good job selling the story.
I did enjoy this better than the first episode of Luke Cage, which was a series that took me a bit to warm up to. If not for Cottonmouth, I don't think I ever would have watched more than one episode. It pissed me off when Cottonmouth was killed by mid season as I thought he was a way better villain than Diamondback, who I thought was rather campy. Cottonmouth was just a BAMF! I guess they thought they needed more of a personal and physical threat to Luke.
I'm a fan of David Wenham, and when he finally shows up, I found someone that I thought would be a good bad guy. We'll see how this plays out. The kid is pretty *****y, but that's probably on purpose, and I don't like the daughter either.
The other thing probably bothering the critics is the origin is pretty similar to Batman, Doctor Strange, the Shadow, and others, where someone goes off to train under Eastern mystics and comes back some all powerful warrior. I'll admit this is not a big fresh take on anything, and can perhaps feel like a "been there, done that", but it was entertaining enough for me to continue watching.
Luke Cage I think got alot of accolades, simply because it unapologetically portrays a black hero, going through struggles that many minorites have to go through. And even the main villains are sympathetic as they faced similar struggles as the heor did only made decisions that took them down the wrong path. However I don't think as a story Luke Cage was as smooth or compelling in the storytelling as Daredevil or Jessica Jones. There were ups and downs, but it certainly was worthy of the critical acclaim it received, but for me it was at times very hard to watch, at others I couldn't wait until the next episode.
We'll see where Iron Fist leads, but I have a feeling this is at least a decent enough effort to make him a force in the Defenders and perhaps a Heroes for Hire spin off.