The general feedback I've gotten from the regulars so far has been overwhelming positive. The campaign suits me well as a DM, cause I treat the source material more like guidelines (pirate), but its so well written I rarely have to pull something out of my butt. The box you've constructed for the setting is so all incompassing, I can almost always use something in the book to fit an off rails decision the players make by tying it to an NPC in order to foreshadowing something for a later chapter (the payoffs are pretty great when the DM makes the effort, I'm looking forward to concluding the Ragman sidequest in chapter 4).
The consensus so far is that the campaign is refreshingly non-combat focused. Its so well written that I don't have to railroad the players because they constantly want to see what happens next. And when they think outside the box, there are plot driven devices to reward them with for their ingenuity. The way I've run this (whether its your intent or not) is that combat is almost always optional, but an ever present option. I've never played, let alone run, a campaign where the combat encounters took a back seat to the exposition and social interaction, which is actually a huge bonus.
The biggest downside is that the plot is so intricate that player fatigue sets in faster than usual during a regular session. For a normal campaign, I try to marathon 6 hour sessions every 2 weeks, but the most my group can handle with this much exposition is about 3-4 hours, and that's even including meta game interaction. Having props and handouts are a must to keep the players following the plot, and if I didn't maintain the journal, the group probably would have lost track of what's going on a month or two ago. Keeping the journal also keeps the story fresh in my head as well, and reminds me if I forgot to mention crucial details during the previous session. The hardest thing for me as a DM is creating on-ramps for new players who sit down for the game (in the journal, these are the "rookies" that come from the RHC detatchment, who are running precon characters out of the NPC codex). I can't expect new players to sift through the 40+ pages worth of journaling just to follow what's going on that particular day. Its a little overwhleming for players who miss weeks (it inevitably happens).
I was really hoping that the "RHC Casefiles" would make it back on the development to-do list, cause it would really help with the on-ramp problem for introducing new players at my local game shop to the campaign who just decide to sit down with us for a couple of hours to see what's up. I know that's a complicated feat, as every group is going to progress through the story differently, so whatever you came up with would need to be redactable (maybe the DM can pretend like there are classified lines in the case file that is above the constable's pay grade until they uncover the plot points). Figuring out how to build this product digitally and in hard copy is probably an interesting development challenge in addition to figuring out the right amount of content (Maybe 3 pages tops per Chapter?).
So on the complexity side, chapter 2 in particular, its both the campaign's greatest asset and greatest liability. Its amazing for the regulars, its a nightmare for the casuals who just sit down for a test drive. And its a ton of work for the DM to keep a record of the campaign's progress so the party doesn't forget what's going on in a chapter that they've been playing for 2+ months.
As for the combat encounters, the players liked the fact that you can't just win the combat by traditional "Tank, DPS, Healer, Crowd-Control" tactics. They TPK'ed Episode 1 (Coaltongue exploded) because they didn't appreciate this point, and we re-ran it and the party has taken a much more thoughtful approach to combat encounters ever since. I've been very open minded about letting the party split as a DM, and I've made sure that the players understood I wasn't going to coddle them on the razor edge risk-rewards associated with those sorts of decisions. Character deaths will occur if the players fly too close to the sun. It creates very real tension in the game that's often absent from many other campaigns I've participated in where there was a more "Dues ex Machina" approach to character deaths.
Also, the deep bench of story relevant NPCs is a huge boon to the game. It goes back to what I said before about me not having to make up much. For example, Pemberton is about to be playing a role in an ongoing grudge between the Conservator and Leon Quital. I'm thinking about how Pemberton's specialize knowledge of Steel and technology (ref Act II, which I'm reading through right now) could play into the Conservator's desire to create a contingency against the Steelshaper. I'll probably use that as a plot hook to get the Conservator (or at least Thomas) to be at the Arms Expo at the beginning of Chapter 3, since he isn't a constable and needs a different reason to be there. I'm going to take some inspiration from this episode of MatPat's Film Theory for what that sort of contingency might entail, but I'm open to suggestions as to how to convert this into actual pathfinder game mechanics based on Leon's actual stats:
https://www.youtube.com/watch?v=YTbeRTH7jkg
Let me know if you have any cautions for me to keep in mind as far as future plotlines I might not have read yet, I'm at the beginning of chapter 6 in my read-ahead.
Another example of how having a deep bench helps flesh out the world is the "Bonds of Forced Faith" One-Shot in the appendix of Act II. It was fun weaving in easter eggs from that in Chapter 2 that may or may not ever pay off if we ever run it as a flashback sidequest.
I'll let you know if I get more feedback from the players. I let them know you were asking.