I was completely enthralled by the fantastic world and implied history of Dreamhold. Like Spider & Web, the world of Dreamhold grabbed me and wouldn't let go. Plotkin's ability to masterfully craft such intertwined riddles within a believable (and compelling) magical reality is singular.
That being said, I don't know if this is the best way to introduce a new player/interactor/guinea pig into interactive fiction. While none of the puzzles are excruciating, the final puzzle, and many of the alternate endings are going to remain beyond the limits of the introductory player. To my eternal shame, I even got stuck on the final puzzle and had to hit the hint system (and still didn't understand!)
My other minor complaint is that Zarf obviously has created a fascinating world but the narrative clues are so obtuse and difficult that a player expecting for all the pieces to fall together in the end is going to be disappointed. As an introductory IF piece, having the prose be more James Joyce then Stephen King to me is a curious choice. One of the endings was fairly incomprehensible to me.
As a standard IF piece, though (and I do think the puzzles will provide challenge even to the most experienced adventurer), it's one of my favorites. I just wish, at the end, I understood a little more of the world. To Dreamhold's credit, though, it has given me enough reason to go back in again.