Note that if/when my GM reads this, I mean no disrespect to him at all. He did his best with what he had to work with, which was unfortunately kind of a mess.
Let's start things off on a positive note. There is a GOOD story here unlike a few modules I've played. The NPCs you're supposed to save have an interesting backstory and you legitimately want to help the people of this town. And the encounters in Part 1 are reasonably fun
Now the bad stuff
1. It seems overly bogged down with sidequests that don't really contribute much besides extra encounters. I'm usually inclined to do them since doing the side stuff in the module tends to translate to provide some help in the later stages. The ones we did, didn't seem to do much story or mechanics wise. You could easily have had them just be dialogue NPCs and get just as much info. And it'd be paced better.
2. There needs to be some gate keeping when letting players design monsters. One monster in part two can perform an instant death skill at range that normally can only be performed in melee. As far as I can remember, the GM said there really was no valid reason given for this. Any time a player designs a monster for use in non-homebrew play, Paizo must make sure said monsters conform to the rules of the system. I hate to play Rules Lawyer but no matter the reason, even if the DC is so low you can only fail on nat 1, if a monster is doing things that break the rules, some reason better be given beyond "dramatic effect" as a good friend called it (and I believe they were being sincere I was just quoting them). I'd accept that it uses a special item or something (particularly if it's available on the Chronicle sheet) but a reason needs to exist IMO. That's just my personal quirk though.
3. Perhaps the most egregious problem is the difficulty spike. The first part's encounters were decent, perhaps a bit too easy. Second part's first couple encounters were alright. But then pretty much goes into Bonekeep territory when you encounter the rulebreaking monster. I'm not trying to dramatic I assure you. I'm told one of the encounter rooms is even a borderline ripoff of Bonekeep. (Minus points for ripping from another scenario if this is true btw. Come on, this author is capable of doing better).
What makes the whole thing worse is that you ABSOLUTELY need a balanced party. The trouble is with 4 players, that is insanely difficult if not wholly impossible. You're either going to be sacrificing damage, healing, spell casting, or trap finding. This is one scenario where you need them all. If you go in with 4 players, prep for a TPK (#DimensionDoor) or have some prestige built up. You are better off just going with max players. Not only would it be paced a lot better, but you'll (probably) survive to see the end of a good story.
Scenarios actively designed to get TPKs, such as Bonekeep, are not for everyone. However, they are honest about their intent. Namely to wreck you, especially if you're not an active powergamer. If you go into such scenarios you do so expecting that this will happen, design around it and are more likely to have fun.
Tears at Bitter Manor, IMO, if played with 4 players as advertised, is an intentional party killer scenario that is not honest about its intent when it starts off like a rather normal, if a bit sidequest heavy, module in the first part. Then it literally rips off Bonekeep and then just goes off the rails from there.
To make things worse, it was not adjusted for more restrictive PFS play when it was allowed.
If I want to play Bonekeep, I will play Bonekeep. I don't think I'm alone here.
I give it a 2/5 for being an intentional party killer that hides itself behind a scenario of reasonable difficulty. If being played go for max players and you'll get 3/5.
