but the more complex the milestone-system becomes, the more it resembles an XP system.
I just think my biggest problem is, that I don't see anything wrong with XP and can't fathom why people hate it so much that they would want to use an (in my eyes) inferior milestone system that needs to be tweaked a lot to get similar results.
So I imagine like many DMs I went back and forth on the XP system. At one point I even developed an XP system that kept track of everything such as new locations they travel to (major trade routes, cities, institutions...etc) and characters' new experiences (prominent NPCs, new spells/powers...etc), essentially rewarding the exploration and social pillars. I then dropped all that and for the longest time and just used milestones because I wasn't satisfied with simple XP progression, particularly once the PCs hit the higher levels as the system wasn't matching my story pacing, as it was requiring me to make changes constantly to the XP tables, and I do not like inconsistency, especially if I as DM am inconsistent.
I then got inspired from a couple of threads/posters here (one being
@iserith with his method for Inspiration) and I thought what do I want to see at the table that would reflect the growth of a character and that is when it hit me... characters delving into their personal traits, flaws, ideals and goals. That is real character growth and certainly creates a + at the table.
(1) So being able to earn and use inspiration by leaning on the character's emotional and mental alignment is far more of an achievement than just the slaying of another monster.
(2) Other character growth comes from a sense of accomplishment - reaching ones goals. I do not track the journey as that is the minutiae so that is where milestone leveling can kick in.
(3) And the third way one can gain a level is a specific time-lined event/experience of some significant importance in the story and in the lives of the characters. A game-changer.
And they are all player-facing, although I as DM can instigate number (3) at any time depending on the story.
Those are the three ways that I feel are right for me to progress the characters
for high level play that would also align with the pacing of our table's storyline. But the 1st two, particularly the 1st, allows the players to have some degree of influence which I feel is important and the reward for earning and using all those inspirations, being a level advancement, will encourage players to bring about more of those magical role-playing experiences at the table. Experience points don't necessarily do that unless the player is so inclined.
It is a new system (2 sessions in) and I'm really happy with the results so far (and I believe the players are too).
The inspiration mechanic was a good thought but the gaining advantage was not a big enough incentive, certainly not at higher levels. Tying the level advancement to it is much more of a push for players to utilise the system, at least at my table.
EDIT: The plus side to all this is there is less for me to track and it encourages the players to really think about their characters, and not just focussing on the mechanical aspect of them.