I’ve started OK-ing the new Pathfinder Advanced Player’s Guide for use in the Southern Reaches campaign. I’ve made it through the new race options and new base classes, approving both. I’ve started reading the new class options for the original base classes and have approved them as I do not anticipate anything game-changing from what I’ve read so far. The reading has been slow because they really did a good job fleshing things out and making them workable – but man that takes some reading fortitude to plow through.
To date, I’ve only had some minor adoptions by the players. Thorngrim chose to swap half-orc ferocity for sacred tattoo. A sorcerer from my other campaign picked up two new spells from the APG (burning gaze and dancing lantern if you're curious), and the paladin from that campaign is interested in possibly switching to inquisitor. We might have to do a temporary switch to see if it is a good fit for the character concept.
So, what to do when the game you’re playing released new rules?
There are two types of new rules: a complete new edition or supplemental rules for the current edition. New rules editions can be really great or really a pain for a GM. If the new edition refines or unifies the application of previous rules (e.g., Champions 4th edition to Champions 5th edition), this can be great and the transition fairly smooth. If the new edition is a complete re-write of the rules from the ground up, like D&D 4E, then you need to decide with your players whether or not to use the new edition or stick with the old one.
In olden times, it was pretty much assumed that the new edition of the rules would eventually be adopted (grognards notwithstanding). With the introduction of the OGL and the retroclones, plus a vaster array of base game systems to choose from, this is no longer the case. It is much easier to stick with older rulesets when the primary manufacturer moves on, especially if your group plays a form of D&D (which is statistically very likely). If you are playing a game that is not covered by the OGL (or something similar) then things are a bit more dicey. Hard to get new players involved if they can’t get their own copy of the books, especially if any length of time has passed since the game went out of print.
From the GM perspective, adoption of a new edition boils down to this: are the advantages of the new ruleset greater than the aggravation of having to re-spec every NPC and monster in your campaign? Depending on what style of campaign you run (fixed length versus perpetual), this conversion process can be a major effort or a titanic effort. You also need to take into account how your players feel about the new rules and what will happen to their characters as part of the conversion.
There are several ways to incorporate a new edition. One is to just take a break from running that campaign, let someone else run something for a while, and convert everything wholesale. This could be modified by just converting things immediately involved and do the rest as necessary, but this seems to just draw out the aggravation. I feel a clean break is better for game play and the GM’s sanity. A possible sideways step is to finish out your current story arc, invoke a major shift in the way the world works, and restart with new characters elsewhere and/or elsewhen. Living Forgotten Realms has done something similar to this with the Forgotten Realms. I have a friend who is in the process of doing this for the second time for his homebrew campaign (2nd to 3rd ed AD&D and now to the Pathfinder RPG).
Now what about “just” a rules supplement?
I’m thinking about the Advanced Players Guide for the Pathfinder RPG, but this could also include adding Unearthed Arcana to AD&D or the Supplements to OD&D – really anywhere you have new rules for existing classes, new classes, new spells and/or powers, or alternate rules for combat or something else being added to the core ruleset. Here the GM’s work is a bit harder. Do you accept it all as written and hope for the best? Do you pick and choose what you want and leave the rest?
The answer is: it depends.
One of the issues with D&D 3.x was unfettered rules bloat. If you, as a DM, allowed everything published into your game, you fairly quickly achieved a singularity and the whole thing collapsed in upon itself. This led to either picking and choosing or house ruling stuff. I prefer running the rules as written, so everyone has the same rules. As a result, I am reluctant to accept rules piecemeal, but have there was a clear benefit to doing so.
With the APG, I’m leaning toward adapting the whole book as-is and then house-ruling anything that becomes problematic. From what I’ve read so far, things seem fairly balanced overall with minimal power creep, if any. Again, this leaves everyone in the group with access to exactly the same set of rules, rules that seem to have been written with balance (not word/page-count) in mind. Your mileage may vary.
I think that's enough rambling for today.