Jessica Jones started off good, got a bit lost in the middle (felt like a bunch of filler episodes sapping the momentum) then finished strongly, I thought. It just needed a shorter run; 8-10 episodes instead of 13.
Luke Cage started off brilliant, then took a nosedive mid-season. It got progressively worse each episode, and I only tuned in to the next in the hope it would pick up. Really not quite sure what the Diamondback ******** was all about.
To an extent, I think Daredevil suffers from being slightly too long as well. Not as bad as JJ, but both seasons could have been tightened up a little if they were cut down to 10 episodes.
I'm hoping this will be more along the lines of DD. I think the trailer looks good, but then I've thought that about every trailer that's been released for the Marvel/Netflix shows. I remain optimistic though; for me, the highlight of Daredevil is the fight choreography. Iron Fist should provide plenty of potential for great scenes.