Chalk me up as one "against" the Kingmaker Adventure Path. I'm midway through DMing the 4th adventure, and it's mostly fallen flat for my group.
I think an APs success can easily vary from group to group as some of them fit more to one group's tastes and style than another. I think it is a large contributing factor to why you'll see one person raving about a particular AP and another person saying it is the worst AP ever. Group styles differ so what works well for one group can work poorly for another.
I think your post was a great review with thought in it, so please don't take my replies as trying to change your mind, just as providing another viewpoint or how we have or plan on handling some of the issues you've mentioned. (note: you are much further along than the group I am running, so bear that in mind as well).
Retreater said:
1) If everyone doesn't get into the kingdom building aspect, you're going to have several players sitting around for an hour or so of each session doing nothing but being bored. (Unless this is all handled via email, but that's been hard for us to coordinate.)
I let my group know up front that the campaign including a large kingdom building mechanic and had buy-in before starting the campaign.
If everyone ends up enjoying the kingdom building, then no problems. If we get a half and half mix, we will use our group's message boards to handle kingdom building between sessions. Our message boards are well established and see active participation between sessions, so I don't see any issues with this option for our group. If no one likes the kingdom building aspect then we implement the kingdom building in the background method mentioned in the AP.
Retreater said:
2) Based on the first mass combat battle featured, the mass combat system so far has been a little "wonky." The party easily overpowered their rival army.
I still need to study this closer. As we draw nearer to it, I have considered using the Warpath rules to add some depth to this element. I will decide as we draw closer to this phase in our group.
Retreater said:
3) If a player becomes the ruler, that person can bully around the other party members. More of an interpersonal issue, but it's still there.
I don't see this as being a problem in our group. Certainly a possibility in other groups though. We'll see as they get established.
Retreater said:
4) It's been very difficult to build up the kingdom, particularly to get Build Points. Every turn (which takes about 15 minutes) nets about 5 Build Points. (It takes something like 10 to build one section of city wall.) Therefore the kingdom building aspect is very slow and tedious.
I have heard that managing the kingdom is a fair amount of work. I suspect we will be using the 'do most of the kingdom building between sessions' option I mentioned above, so I don't suspect it will impact our face to face play time much and be done over the course of a week.
Retreater said:
5) Be prepared to have your kingdom information on a spreadsheet. It turns into an accounting exercise very quickly due to all of the different modifiers. (You'll be making what amounts to DC 100 checks regularly later on in the Path. So if you can imagine tracking all of your modfiers - it gets a little crazy.)
Definitely planning on using one of the available kingdom building spreadsheets from the Paizo forums to make this easier to track.
Retreater said:
6) Concerning the adventures themselves, I've found them to be of average quality at best. A general comment is that they're not adequately challenging. Meaning that you can be 1st level and run into 1d4 trolls or 11th and have fights with CR 2 bullywugs (okay, boggards). The overall feel is of a bunch of disconcected, one or two room adventure sights (most of which aren't mapped).
At the early stages I have been fine with the quality, though I do intend to add a bit more depth as we roll forward to keep things tied together and add to the feel of the world.
I don't have problems with the mis-matched encounter levels one can find. It is during the exploration phases this happens and it stands to reason that one won't always be running into the encounters of appropriate level when exploring. Many folks also just leave tracks of some big critter that is overpowered to show that one is about, but not actually throw it at the party to help with this.
I know this style does not match everyone though. I've seen the heated debates on whether a DM should ever throw something the party should run from instead of fight or not. I usually fall into that being fair game, but I know many do not like that approach. If you (or your group) fall into that latter group then I can see why the overpowered random encounters are off-putting.
Again, I am not trying to change you mind - not all APs work for all groups due to differing playstyles. I just wanted to provide another perspective for those reading. What works for my group certainly may not work for someone else - true for most of the advice on these boards.