I had an interesting experience with my first game playing Bringer of Dreams and Nightmares.
So far, I've found the Fear mechanic to be interesting, fun, and critical to the game progress. Getting the extra bonus before the Invader Phase is a great reward that really adds to the flavor of the game, and sometimes provides a key tactical benefit. We quickly found that earning one or two Fear cards each round put us on a good path to victory. We'd not yet seen an outright Fear victory, though we'd made it to Terror Level III on several occasions.
So, I figured that Bringer of Dreams and Nightmares would be an outright asset to our victory over the Invaders. At first, of course, I was generating huge amounts of Fear, regularly earning at least two Fear cards each round. However, after seeing how helpless Bringer was at keeping the Invaders at bay on its home board, letting Blight get out of hand, I started to pick up a couple Defend powers. This had almost the opposite effect I wanted: whenever I used the Defend powers, my Fear production dropped off precipitously, and I wasn't actually good at anything. So, I left off the Defending and resumed Fear - generating it at an accelerated clip, and despite an ever-increasing level of Blight and torrents of Invaders, we won a Terror victory.
I found the win totally unsatisfying. Playing a game with Bringer of Dreams and Nightmares turned the game into a matter of playing cards that let us move some counters up, until we moved enough to win. We simply had to try to do this before the Invaders did too much. The board, what the Invaders were doing, the other spirits, Presence - none of it was really relevant to Bringer of Dreams and Nightmares. It just had to care about ticking up these little counters until we reached VICTORY at the bottom of the Fear Deck. In some ways, that's thematic to the spirit - but it made for a very unsatisfying game.
Playing Bringer of Dreams and Nightmares convinced me that Fear should not cause an outright victory. It absolutely should make the Invaders more demoralized and make victory easier over the course of the game, but I think having "You win!" at the bottom wasn't really as fun as it could have been. I would have liked to uncover an effect at the bottom of the Fear deck that has the Invaders running in terror from the island, the spirits, and the Dahan, but continue the game until the "no cities" condition from Terror Level 3 is met.