I would like to know people's favorite character presented in that AP as well as any interesting stories involving them.
I personally like Vadoma Gall the best. She seems like a great fool for the party.
They feel like a fun showcase of Paizo employees' PCs. I haven't used any of them.
I used the Terrible Tup as the messenger for Hargulka when I ran Kingmaker.
I didn't use any of them for neither Hell's Rebels nor Mummy's Mask but I'll take a look through them again before I run Crimson Throne.
But unless you're looking for either an NPC that isn't in the AP / module you're running or you want a more fleshed out NPC to add to the campaign you're running, I see them as just kind of filler. Not a terrible idea, but not all that useful either.