Though it has its moments - usually not far from when Jessica Jones or Luke Cage are on screen - The Defenders is set to be a little more divisive than Cage, Jones and Daredevil's first seasons. It's no where near as disappointing as the boring Iron Fist, but it definitely struggles with some of the same sluggishness that beset the non-Punisher parts of Daredevil season 2 (which might have a lot to do with Elektra's return, frankly).
That said, Sigourney Weaver is excellent, the chemistry between all four leads is great and there's enough in there to suggest that there could even be a great Heroes For Hire show uniting Luke Cage and Danny Rand if they capture the right tone. That's no small success in itself given the reviews of Rand's own show.
inevitably, Netflix's latest show is steeped in the lore already established by the five seasons to date, with reappearances of most supporting characters, a furthering of the mythology of The Hand (sorry, but it's time we moved on from them for a while) and little call-backs to important universe details. There are Easter Eggs in that respect, but there are also references and Eggs from further afield, taking in the comics as well as other pop culture sources.