My party played through the whole series and eagerly aniticpated the climax to the kobold storyline, as did I after I spent some time massaging Zalath's stats and making him a badass wizard boss fight.
However, I found this adventure to require even more planning, preparing and hole-plugging than the previous three. The party could enter the ruins of the keep, which they absolutely should otherwise they would be cutting this adventure in half, only it ends in a very unsatifactory dead end. There are lots of details which raise questions; bodies, scorch marks, a plinth with something missing... but, again, absolutely no context is provided for the DM.
If you're not careful to really do your homework and plan the session out with your own answers and depth, you will find yourself pummelled with questions and confusion from any party that is remotely inquisitive.
Having done this planning and fitting the adventure into my ongoing campaign, I managed to make something pretty epic to round off the series with. My problem is that I just didn't feel like the adventure, as-written, was working with me.
I look back and wonder, what was in those letters Chariz recieved? What was the point of sending the party to collect an item underneath a stone circle? What was the battle that killed all the kobold? Maybe the answers are there, or purposefully kept loose for you to make it your own, but instead I anticipate that they just weren't thought through.