Played this today with a mid-tier group that ended up playing up with the 4-player adjustment. We certainly went the light-hearted route. One player commented "It's hard to feel scared when I'm rolling dice."
I agree with many others who say this wasn't that challenging, but it opens up a lot of possible fun. The GM mentioned some of the mechanics were clunky so I'll have to read it and perhaps run it myself to know the entire story.
I am only somewhat satisfied with having played this scenario. There is simply too much of the mass combat. It's not role-playing; it's a board game. One instance of it would have been ok. Even if the instances were broken up by something else other than mass combat it would have been better.
The rules are /really/ complex and trying to get people to learn them during the space of a session is really tough. These rules need to be made public in advance (unless they already are) so people can study them, especially if Paizo plans more of these sessions.
Some of the rules don't make sense. Charisma is the only stat that matters to commanding armies? So a bard makes a better commander than a fighter? Silly.
Broken windows scatter glass in the opposite direction you break them from? Silly.
I played at tier 3-4 and the final fight went fine, but it could have been a lot worse. It's a tough opponent, maybe too tough for the tier.
In the end it's ok. Honestly? I'm not sure I want a lot more of it. If you are going to do more mass combat please limit it to once per scenario and let people get back to playing their own characters.