I didn't expect the revelation of who Kylo Ren was, but I wasn't shocked by it. And I don't think it was lazy or tired to have the story go there, I think it's very valid. We need the future movies to fill in exactly what tilted him toward the Dark Side, but I can get behind the idea that he would go there, given proper motivation. He grows up hearing about the Jedi, so he's curious about the whole Force thing, having inherited the ability to use it from Leia. At an impressionable time this mysterious Snoke comes in and confuses him, he turns to a warped understanding of his family legacy (it seems he apparently somehow doesn't know Vader turned back to the Light in the end) and takes it on himself to fulfill that part and not Luke's part. So he essentially covers up anything going on in the present and only looks back a generation to make his path, becoming obsessed with Vader as a Sith. Which is why he wears the mask; I was right about that! He doesn't need it, he's emulating Vader because he wants to be like him. And the scene where he was talking to the mask was a new look at this we haven't seen before; instead of someone trying to stay good against temptations of the Dark Side here's someone who actually wants to take the Dark Path, believes that is the right way, but is struggling with being tempted back to the Light. I really liked that view of the other side.
I liked Kylo's lightsaber, it was a great touch of detail that the blade was jagged, not properly focused. That makes perfect sense. He's pretty much self taught right, he got on the Vader kick and started mimicking whatever he thought was appropriate to follow in those steps, but had no training in how to build a lightsaber so it's just functional, not refined.
I liked the vision of what emerged from the fallout of Return of the Jedi, though I wish it had been filled in a bit more. We got the basics, the Empire was replaced by the New Republic but remnants reformed into the First Order with the Resistance trying to hold them off; but some details of how all that came together would have been nice. I liked that the Sith don't seem to be the leaders this time around, they and the First Order are working together, they're not the same thing. That's something that gets missed in the previous movies sometimes, people think the Sith equals the Empire but they don't, the Sith just happened to be controlling the Empire at that time.
I had just a couple nitpicks lore-wise. I wasn't very into Finn fighting Kylo. Effective lightsaber use requires some affinity with the Force. I guess you could say that's why he was beaten relatively easily, but he still put up a better fight then I would have thought he could/should have. Same thing, but opposite, with Rey. Although she clearly not only has the Force but is very strong with it as she was able to learn to use it so quickly, it still seemed a large leap that she would become instantly proficient with a lightsaber the first time she used one. But I grew to the idea some by remembering that she has considerable experience fighting with that staff, so some of that training could carry over.
The one thing I did not like was the appearance of Luke's original lightsaber (so Anakin's original, actually) and blatant refusal to explain how it got there. That was definitely lost forever after falling out of Cloud City, clearly they avoided an explanation because they couldn't think of one.
I heard no spoilers on anything, but I was independently certain Han was going to die; I didn't want it to happen I just didn't think it was possible for it not to. I was concerned about how they would do it, if they were going to they had to do it right, and I think they did. This was a meaningful way to have it happen. I thought the scene was well constructed, it was clear from the dialogue what Kylo meant (we know from RotJ that what one needs to do to complete the turn to the Dark Side is kill your father) but it was also clear he was genuinely struggling with it, because he wasn't fully convinced by or committed to the Dark Path yet.