I don't know if my group is having fun with an NPC's harrowings in Jade Regent ... yet. But as GM, I'm getting goosebumps on how random card-draws are working out.
The NPC did harrowings for each PC and the group as a whole as the group set out on a journey. The card readings gave me as GM a whole lot to think about as I plan the rest of the book of the AP. How to slightly twist things to make the readings come to the fore. To a certain extent, the plot is twisting itself!
I will admit, I dealt out the cards for the group harrowing by myself -- and ended up switching two cards, and outright changing one, to make it less dark. (Some would decry that as cheating.) In any case, I definitely came up with a better reading given a bit of time to think about what the NPC would say! When the time came for the reading in front of the players, I had the cards stacked. However, I did the individual readings on the spot, no cheating on the cards, and most of them came out verrrry interesting. (Although I had to stress that the NPC didn't fumble for an interpretation of the cards like I did, flipping through the rulebook!)
In terms of making the readings fun for the players, I went with a lot of atmospheric stuff -- incense, flickering light, cups of tea (but no tea-leaf readings), that sort of thing. I strongly recommend buying the actual deck, rather than going with dice, if you haven't.
PS: I just remembered: does CotCT have some specific Harrowing deck mechanics? If so, I'd ask in the AP forum, if you haven't. (They're hidden under Pathfinder rather than Pathfinder RPG.)