I wasn't planning on getting this, but all buzz made me want to check it out. I did and decided to buy. I have only skimmed it so far, but here are a couple of quick thoughts:
1) Acererak is a lot tougher than a standard lich. I think he is closer to what people think of when they think of liches.
2) The atropal is interesting. I would have probably given it innate spellcasting, but it has some interesting abilities that could be troublesome.
3) Didn't realize we would be getting a statblock for Volo
4) The pull out map is nice, I didn't realize it came with one.
5) I don't like that all the monsters from VGtM that are in the adventure are reprinted here. I wish they had used that space differently. Personally, I think it is OK to assume you need to own VGtM and the MM, but I know others will disagree.
6) Glad to see the nine gods are "false gods," I was wondering how A could shackle nine gods.