I ran another planescape campaign almost immediately after the previous one. This one was an evolution, building on the feedback from its predecessor and it was planescape because you can't get enough of a good thing. Here's my retrospective on what worked and what didn't.
A group of planar and prime PCs meet in the restaurant at the end of existence to pick up a job from a representative of the Planar Trade Consortium. The job was the first in a series of fetch quests for one of the Golden Lords of Sigil retrieving rare items from across the planes. I had the idea for some side quest plot hooks but purposefully made them doable while on the main fetch quests so as to not lose focus. I also introduced a faction points scheme to encourage involvement in Sigil's factions. Characters who promoted their faction earned more powerful abilities as belief in their cause grew.
What the Players made:
As it happens the players never minmaxed the faction points scheme by all joining one faction. Instead they pretty much camped out in their own factions and the party was a constant philosophical engagement as they strove to sway NPCs to their side. While the roster changed considerably across the course of the game, with many players retiring their original characters to start a new one, almost everyone got a good send-off (RIP Sigrun).
The game proceeded pretty much on track. The players were engaged by the fetch quests because each one presented a different problem(retrieve a solid rock from the plane of fire, capture the moonbeam of a remote Prime) while also relishing the opportunities to roleplay against one another in their factions. There was actually some player versus player but it didn't end acrimoniously, in fact it was fairly mutually agreed to be a good way to go. Most of the problems players had in engagment came when scheduling issues arose which are up to me to solve. I probably could have been more available for catch-up sessions.
Comments from the players:
Focused: The players felt this campaign was much more focused while still allowing them to pursue their own interests
Opaque: The faction points system was a little hard to interact with as there were no clear guidelines to gain points beyond "Live your faction's philosophy"
Ending: The ending was again rushed because narratively my campaigns have endings like Lord of the Rings. A climactic battle followed by another two hours of people talking rather deflates the ending so I always cut out the talking.
In summary we played a Planehopping game with the philosophical and balderdash elements to the fore. The game was a significant improvement over the first and thus, less to talk about. What matters always is making it better.