It's not bad.
The action's entertaining, the characters interact well, it's always good to see more of Krysten Ritter as Jessica Jones, and overall the series is far more focused than most that have come before (which is surprising given there are now 4 'heroes' to deal with).
Unfortunately, there's little to it beyond that. The story, though focused, isn't particularly interesting, Sigourney Weaver's good as the new villain, but doesn't get a lot to do, and the hole 'The Hand' thing has never really worked anyway. And the coming together of these four iconic characters doesn't raise so much as a mild tingle as two are boring, frustrating dim-wits, Daredevil's a badass, but is otherwise flat beyond a few wry lines, and only Jessica Jones is genuinely compelling, and interesting to watch outside of the fight scenes.
I am, however, given hope for the future of the franchise because they do seem to be aware of the problems of the past. It was too late to fix Iron Fist's character for this series, but at least he's called out by the others (especially the always entertaining Stick) for being a childish, entitled dip-shit. At only 8 episodes long, there's little filler beyond the first episode (which does drag, so be prepared for that initial hurdle), and it's the first of these I've been able to watch in (almost) a single sitting. They even addressed the botch job they made of Elektra - and the child-of-destiny crap that is the hallmark of the lazy writer - with a twist late into the series that I did see coming, but not in the way they did it, or the direction they then took it in.
Overall, I'd rank it 4th in the MNU:
1. Daredevil & Jessica Jones
[JJ is by far the best written, with the most interesting and intelligent story, and compelling protagonist, but DD was more entertaining and bore the burden of both getting this whole thing started, and making up for what had come before better than I could have hoped. Plus both had awesome villains that out-do anything in even the MCU, including Loki (come at me, brah!)]
3. Daredevil season 2
[If it was just the Punisher-focused stuff, this would be alongside Jessica Jones instead of season 1, but the whole thing was brought down by the Elektra/Hand crap]
4. The Defenders
[See above]
5. Luke Cage
[Great ensemble of villains, and supporting cast, but lazy writing, good ideas that went nowhere, boring action, and a frustrating protagonist]
6. Iron Fist
[If only I could rank it lower...]
