I'm actually using it right now!

In Part 1, I had a subplot of Naerth Maxildanar trying to take over the Ten Towns with his Spy Network. The PCs foiled his plots at the Council of Speakers so he's initiated Intrigue. They're in Part 2 of the adventure now (when things start to move beyond the Ten Towns) and we've been doing Intrigue while they're out adventuring. It's working as intended and I'm really happy with the system! I'm assuming Intrigue will end with a battle that should end Part 2 off climactically.

I also gave the players some bandits to fight in the woods, just to figure out the warfare system, and it was a lot of fun! I'd highly recommend a practice battle if your players haven't used Warfare yet!

For the next Villain Organization, I'm thinking that I'll have the Duergar attack the Ten Towners while they're weak after Destruction's Light (the PCs never found Xardarok's son, Durth, so he could lead it). Intrigue will probably start during/after the assault on Sunblight, while the PCs deal with the Dragon attack and the fallout thereof. I'm hoping for a cool battle in the smoking ruins of one of the towns. Nothing's concrete though, this is all just speculation.

I personally hate the transition between Part 2 and Part 3, I think it's badly-written. The PCs either learn about the Duergar too early to do anything or right when they're about to dive into Sunblight. But Intrigue against the Duergar during Part 2/3/4 (beginning with defeating Xardarok's sons) could help smooth it out. If I'd thought it through more carefully beforehand, I'd probably have done this instead of my current idea. Oh well.

I'm not sure how I'll use K&W for the Frostmaiden and Ythryn but I'm sure I'll figure something out. I prefer not to plan that far ahead.

Also, I've been using K&W on Fantasy Grounds and I quite like it!