Just finished this up a couple of days ago. This was a fairly action-packed adventure and my players enjoyed it. They probably had the typical response of "You're hiring us to kill kobolds? Did you run out of one-legged grandparents to do the job for you?" to "I'm going to genocide every kobold tribe I see in the future" by the end.
A variety of situations where the kobolds use traps and superior tactics to give the PCs a challenge, and a number of those situations where the PCs can use intelligent tactics to give them the fight right back. Starting descriptions of areas focus on the tactical stuff first, with loot and fluff at the end. This seems to work better than a lot of D&D descriptions, which have struggled with how to convey information on each location for different purposes (I think 4th Edition separated descriptions into combat stat sections and environmental sections, which was close, but slightly more confusing).
I think there was a little too much padding for me around the middle, and I cut some of it out. Some of the parts were less "challenging" and more just "PCs get whacked and take damage". My favorite parts were the initial Crag Kragen estate and the keep entrance to the final dungeon because they were set up in a way to punish people blundering ahead but be perfectly reasonable if you used good tactics. For example, my wife's Cleric (Trickster Domain) used her stealth powers to sneak up to the keep, Stone Shape their way into one of the towers, and then take the towers out. The kobolds were split up and surprised, and thus easily killed. Simply charging the gates would (as the adventure pointed out) be a lot more dangerous to the party. Some of the other parts were a little more just "You see a shadow and get hit by bombs/sniper bullet, take X damage and roll for initiative!", which got old after a bit. I ended up narrating my way through 1-2 encounters of the Final Dungeon because it was also pretty similar to the beginning of the adventure at the Crag Kragen estate: "You follow the Sorcerer through several rooms where kobold commandos charge out at you from hidden locations, pepper you with arrows, and the Sorcerer lobs fireballs at you. After sustaining X amount of damage, you find potions on the kobold corpses that heal you for conveniently X amount of damage, and the Sorcerer has ran from you up into a room with four central pillars ahead".
I'm wondering if groups with melee-centric characters would enjoy this adventure less. My players rolled up their characters somewhat randomly, and they all ended up with ranged builds, even the Fighter and Rogue. The only real melee characters were the kobold zombies that my PCs kept animating (seriously, the Wizard, Cleric and Bard all had Animate Dead). Apart from the few drakes, the PCs mostly fight kobolds and dragons who attempt to ambush the PCs and attack them at range, and I'm thinking that a Monk or Barbarian might get frustrated with the whole thing.
Overall, though, lots of fun!
[5 of 5 Stars!]