I found Finn as Danny okay at first. Though by episode 9 I got really annoyed with him. But I guess that's more the writing's fault than his. I didn't like him being such a naive, tantrum throwing child, who keeps running into situations with no plan at all, and just wings it all the time. Hopefully whoever is in charge of the Defenders, has a better handle on the character. Though some things I can't blame on the writing. Like when Finn has to act all confident, well, more when he has to show authority, he comes across like a dick. He is just not likeable in those moments, or really convincing.
But my main problem with Finn is that he doesn't really feel threatening at all. He's supposed to be K'un-Lun finest warrior. Grueling training for 15 years, where every day was a struggle, the immortal weapon, the Iron Fist. He doesn't sell it. Not even remotely. And that just takes me out of the moment every time he fights.