I ran this module the other day; it went very well! The players were scared of the city of silence so they never entered, and after bumping into the band convinced them to go check it out (for it's amazing acoustics on the outskirts!).
They hadn't even encountered the harpies, so when they went back to check in on the band they were horrified to find the harpies ripping them apart. It was golden.
I was afraid it might go on for a long time with all of the combat, but my group is pretty good at not pissing people off so they only ended up doing one combat (freeing Malydra unknowingly) even though they visited almost all locations. It would have been two with the big climax, but to keep it from spilling into another session I skipped that one.
It was great though, the players wanted to kick Karazar's ass the entire time, and made a lot of friends complaining about him. Fun for me, fun for them!
The only thing that was a bit hard during planning was figuring out how to handle skipping the players ahead to Karazar's place. It felt like it would be a bit weird to montage the investigation. Luckily my group decided to give gold to an addict and followed him directly to Karazar, so I got out of dealing with that haha.
Another thing that was a bit of a bummer is that a player ended up grabbing Karazar's poetry book, which is hilarious but also she seemed bummed. They're heading to a city full of posers soon so I'm going to let her sell it to some hipster that hates mainstream poetry. If I did it again I'd probably swap that out with something valuable. I liked the varying qualities of loot, just not the valueless one.
Everything inside the bottle though was golden, very very good.