I feel like I have a lot of these threads where I test out a new subsystem and post my experiences....
Social Combat is the new thing that came along in Ultimate Intrigue, and within the section is a new mechanically defined wordplay game. There's a ton of different ways to play, so I totally suggest checking out the section (pg 176) because it's pretty open ended intentionally.
Verbal Duels revolve around three main mechanics: the skill system, the initiative system, and their own take on numerical stuff (you'll see). All skills are only calculated using (ranks) + CHA +3[for class skills]. Any additional bonuses you have beyond that (not including the actual ability score you use, since all the tactics use CHA) need to be totaled up and divided by 3. That number you get gives you a number of edges. Edges are the exact same thing as the Advantage system from 5e, meaning that you can spend one to grant yourself a reroll, and the DM is encouraged to award them to players for inspired role playing. That isn't to say that you cannot get a numerical bonus to a roll however, as certain tactics specifically counter each other, conferring a +2 bonus. There are also ways to attain bonuses from the audience, depending on whether or not you can sway them to your side, for another +2. They can also be swayed against your opponent, giving them a -2. Within these basic mechanics you understand the general idea of the gameplay. You roll initiatives, using your modifiers as normal (Improved Initiative, etc) only substituting your CHA for your DEX. Then you have a Determination Pool, which is your HP for verbal duels. Every exchange has an opener, and as you progress the turn counter goes up to determine the ante, which is the amount of 'damage' you take to your determination. Once one side concedes, or their determination hits zero, the duel is over.
The good: The tactics are done very well, and include a lot of different and more uses for skills than you would have thought. You can basically turn any skill check you have into Diplomacy, if you can play it off as knowledge on the topic. This means players other than the diplomancers in the group can engage in social situations.
It gets engaging, and my players were very involved in deciding who's skill to associate with which tactic while it was happening.
The bad: The math of the system isn't right. It plays too slow because the damage scales linearly, and there's no variable. The system basically writes magic out of the game, which is something I was not happy about. I want to put an 11th tactic in which can include casting a spell, or using an ability to prove a point, call it Demonstration or something. Recalculating everyone's skills sucks. Edges were hard to determine, and the math was annoying, and my players forgot about them (so did I). Forcing everyone to use a skill they are good with using their CHA instead of their good modifier kinda defeats the purpose of including the non CHA based characters imo.
Conclusion: As written, you need to actually invest a lot of time into making it work, which could derail gameplay more than it helps.
My Solutions: I nixed the edges system all together, and I don't force everyone to use their CHA. You can use your skill modifier straight off the character sheet, no recalculating. The ante needs to scale either quadraticly, or using a better scale. The Fibonacci sequence might actually work better. These changes made it a lot easier to jump right in straight from gameplay whenever there's a big conversation coming up (like with guards, trying to get into some place, or a king/patron discussing the terms of a reward). Just have whichever player thinks they have the best opener roll an initiative check using his CHA mod instead of DEX and you're already in.
Oh, and I hate Ironclad Logic flat out shutting down Student of Philosophy and the Empiricicst, which killed some character concepts I had. The feat had a lot of potential.