I've read some accounts of games run with ToC, and two things jump out at me:
1. the rulebook suggests that combat is especially lethal. However, the in-game accounts don't make it sound very lethal. How does combat generally run? For me, an ideal system would be one where human enemies (thugs or cultists or whatever) aren't especially lethal, but monsters are. Dying to a random cultist with a revolver is lame; but being able to trounce monsters that are supposed to be mind-shattering monstrosities is also lame.
2. CoC awards SAN for successes in-game, and RPGs tend to reward players for building "wandering adventurer" characters. The experience I have had in CoC has been of big campaigns (MoN, etc) with PCs going from one location to another, not returning back home in between (wherever that is), and relying on SAN awards at the end of each location or whatever to keep PCs more or less afloat. My campaigns have tended towards pulpy, globetrotting, high-adventure antics. I'm not complaining - it's fun.
ToC looks like the rules for sources of stability and such both force PCs to spend time at home between adventures, and make them vulnerable by having there be families and friends and such the bad guys can kill or whatever. It seems to make the vulnerability even across the party - as opposed to the loner hobo being immune to that, more or less, while the aristocrat is the opposite.
I haven't had any trouble with the problem the GUMSHOE system is intended to solve - PCs missing clues - because I try to run/design investigations with multiple paths (if you are missing anything in MoN, the problem goes beyond blowing a role every now and then), and am fairly good at making up for PCs missing things.
However, I want to run Tatters of the King and while to some degree the linearity might be a problem - the story is linear and tightly plotted, and I worry they might miss clues - a bigger problem is that TotK seems written as though assuming the PCs are normal human beings instead of adventurers. There are parts of the campaign where there's nothing to do until an NPC sends a letter or whatever, and under the model my CoC campaigns take, I suspect my PCs would (literally) try to blow the story open.
So, if the ToC setup with sources of stability etc means that PCs are less likely to assume that arson is the best solution to any problem, that is what I would be looking for...