I've got a lot of nice things to say about this module, but unfortunately it's going to take a while before we get to them. Right now, I've got a problem with foreshadowing. We've barely finished talking about Chekhov's Gun, and Thunderspire Labyrinth is doing it wrong already.
Thunderspire Mountain is, as the name implies, a huge mountain whose tip is constantly swathed in swirling storms. Within the mountain lies the ruins of the abandoned minotaur city of Saruun Khel. The minotaurs apparently once ruled this area, until a civil war broke out between followers of the demon-god Baphomet and cultists of Torog, the King Who Crawls. Now their once-mighty streets are infested with hobgoblins, duergar, and worse.
Players don't necessarily have access to this information up front. However, the module isn't subtle in showing off its flavour. The players approach the undermountain through "a 50-foot-tall stone archway hewn out of the mountainside", on each side of which "a towering minotaur statue stands [...] glowering down at travellers."
This is foreshadowing. This is giant letters writ across the shape of what is yet to come, spelling out "Here Be Minotaurs" in stark red writing. This is telling players that Thunderspire is watched over by ancient guardians, and those guardians have the head of a bull.
Even as your players pass beneath this archway, they'll be sharpening their weapons and patting each other on the back and declaring, "Oh boy! Minotaurs!" Minotaurs are a classic enemy, yet not so overused as to feel cliched. They're a great theme villain for 4th Edition's second outing, and the idea of taking on a tribe of these beasties in the claustrophobic setting of a ruined underound city is enough to get you really excited about what's coming up.
Unfortunately, it's not to be. There's not hide nor hair of a living minotaur to be seen throughout the length of Thunderspire. Again and again, the module serves up minotaur statues, minotaur corpses, minotaur carvings and minotaur loot, but the cow-men themselves are nowhere to be seen. Thunderspire marches proudly through hobgoblins, duergar, gnolls, and a very human master villain without ever firing the gun it spends the entirety of its flavour-text loading.
It's not the last time we're going to see this kind of misguided foreshadowing, either. We're going to see a beholder-themed Chamber of Eyes that's missing a beholder, a Horned Hold devoid of horns, and a Tower With No Doors featuring a very prominent door. There's the mysteriously absent Mages of Saruun whose vanishing is never resolved, no less than five different evil gods to offend who never take their vengeance, and by ironic contrast the final villain comes completely out of left-field with no solid connection to anything that's gone before.
On the plus side, though, we're going to get to see a dragon...