I just finished playing this! Excellent job to everyone involved. The puzzles were great, especially Map10's.
However, I have to say that Map10's arena fight at the end was a little much for my taste, and following that fight immediately with a slaughter-battle in the hub and then another slaughter map after that to finish the wad felt a bit repetitive.
Other than that, I thought it was fantastic. The hub reminded me of Crash Bandicoot 2, with all of the decorations around each of the portals. The Abandon Observatory may be my new favorite map for Hexen or any iwad ever. I loved how it just drips with atmosphere and beautifully diverse lighting, as well as having a very satisfying flow to find all the puzzle items.
Again, thank you to everyone who helped make this. I would happily play a XUMP II