I just started running it, but I'm very excited about how it is slotting into my own version of Fallcrest and the PC's backstory:
The Tiefling Wizard is a member of House Naerumar, and was asked by his father, Orest Naerumar, to deliver the tiefling blade to Gendar the drow. He became an "adventurer" to encourage people to view the tieflings as more heroic and less sinister, and now he's discovering that his father has business relations with drow?
The tiefling also doesn't know that his former girlfriend, the younger sister of the female Tiefling running the Azaer business in Fallcrest is now running the Azaer business in the Seven Pillared Hall. The other party members have been there, but none of them know her. He knows her, but hasn't entered the business. He broke off their relationship abruptly after a disconcerting arcane experience caused him to question his life, and she resents it (as he never shared this with her). This is also a source of friction between him and his father, and between him and House Azaer, as they had hoped for a closer mercantile relationship as a result of a marriage.
The elf is adamantly opposed to any dealings with the drow, as he feels they are all slavers and evil. Of course, the drow they are dealing with is actually not evil (just unaligned).
The elf is also the only survivor of a small village razed by goblins and hobgoblins. He still doesn't realize that the goblins of the area were egged on and assisted by the Bloodreavers to gain more slaves. His older brother was one of the slaves captured, and he will discover his signet ring in one of the "random" encounters (as his brother escaped captivity, but did so on his own, and perished in the dark of the Labyrinth). This could embitter the elf against the hobgoblins and duergar further, or possibly help him to become more open and trusting with his own companions (as his brother would have survived if he had not struck out on his own, possibly).
The tiefling wizard was also originally secretly training to be a warlock, but was frightened by what he encountered, which is why he was a wizard multiclassing a warlock power, and not a warlock. He still doesn't realize that what he encountered was an avatar of Vecna, and until he can overcome his shame and secrecy and share his "sordid" beginnings with his friends, Vecna still has a hold on his soul (despite retraining out of the Warlock power). If he hasn't done this by the final encounters, he will actually begin having the dreams about seeking out the Pyramid of Power.
The halfing rogue, a member of the Swiftwater clan in Fallcrest, is the only unaligned party member. She is going to have a great deal of opportunity to make decisions about her "unalignment" in the Seven Pillared Hall. Will she steadfastly support her friends (moving her more toward the Good Alignment), or make decisions and allegiances based on her own self interest (which might cause conflict with the party)?
The elf will also have opportunities for both revenge againt Torog and the slavers who captured his kinfolk, and a chance to see how the mighty minotaur empire fell through their own embrace of their darker nature and emotions. He can see how the minotaurs turned away from their greatness to embrace their bestial side.
I also really, really like how many of the adventures are more open-ended. Do you find the Horned Hold by entering the duergar trading post and attacking, or do you negotiate, or do you let your rogue sneak in and rifle the desk? Maybe you just bribe Gendar to help you, or wander around the Labyrinth hoping for the best.