I had the distinct pleasure to DM this many times at GameHole Con where it premiered. It is really nice to see the author really took the feedback from myself and dozens of players to further enhance the module!
I have seen this module become 2 massive slog fights that the PC's barely survived or be completed in under 2 hours due to excellent RP, lucky nat 20's, and excellently applied Dimension Door spells + portable hole. That group surprised me and I can eleborate if anyone is curious.
Overall it is a great module and lays the foundation for the rest of the trilogy nicely. (I got to read those as well and buckle up folks!)
Changing the Crystal Skull to be more generally useful to living PC's and adding the whisper skull as a common item were excellent ideas.
Finally, allowing the main armour reward to be druid friendly has made at least 3 players extremely happy!