How do you feel about Experience Points, and how they are distributed?
My general feeling on the topic is that its importance is somewhat overrated, but not too much.
I think the most important thing is the general level advancement speed of player characters, which is determined by the total XP gained. How exactly are they distributed during the game is secondary, not irrelevant but less important.
Personally I started off DMing in 3.0 edition using standard XP rules (i.e. combat) + individual bonus XP for
anything, from strong roleplay to good tactics to right decisions to individual achievements... so in the same session the Paladin could get +50XP for a nice speech against the BBEG, the Rogue +25XP for successfully disarming a trap, the Fighter +100XP for figuring out the best way to ambush the enemies and so on. It was way too fiddly and subjective, and even with its theoretical good purpose (i.e. to encourage players to
play well) it gave me the feeling that it was unfair to other players who maybe were not that good, and could get
discouraged by the competitive aspect of this system.
So I then moved to "same XP to everyone". But I did include XP for surpassing non-combat scenarios, actually trying to make them about as valuable as combat, think 50-50 XP gained from either. It worked quite well, even if the non-combat XP were still essentially subjective.
Next I switched to "everyone levels up when the DM says so", which was actually decided only because I had various published adventures that I wanted to run, so I needed a way as a DM to control the level of the PCs in order to fit with those adventures. Sometimes it meant to speed up the leveling quickly, some other time to stop it altogether. This is the closest I have used to "milestone levelling", or perhaps equivalent to it if those milestones are set by the DM freely instead of being regulated. The only problem I encountered with this approach was that some of my players said they
missed recording XPs, because they found it to be a nice throw-back touch like scoring points in a video game...
I continued with this approach also during 5e playtest years, but in that phase it was always agreed that we were
playtesting and wanted to play the game at whatever levels we wished.
However, when we actually just started
playing the new edition, I decided to use the default XP rules (which in fact, we probably should have playtested too!) and that's because I always want to play with default rules first...
Nowadays, I am still using 5e default XP rules i.e. combat XP only. I believe the real reason is that I just
don't care anymore

I see no reason to change it currently, even tho I always feel like I'd prefer a de-celerating level/XP progression.