I don't know if this is a rant or a request for comments but here goes.
I've been running PrPs on Arx which has been fun; for starters there are always people (so...many...people) which means I never had to postpone things because no one showed up. For another the system is super easy to use - for the uninitiated there's a @check command which is the equivalent of +roll/+dice on other MU*, and since there is no official mechanical system you just roll whichever stats you want, such as say, dexterity+athletics... and that's it. It couldn't be simpler, which was a godsend for me since I figured it'd focus people on posing.
However!
This is hardly an Arx-specific thing but I really wish some players would stop trying so hard to be nonchalant and cool as a cucumber about everything that's happening. Building atmosphere while dealing with a large number of people, most of whom are OOC unknown to the runner, is tricky to begin with without having characters show up literally yawning about the possibility of assassination attempts and demonic invasions. On top of this I introduced challenges (tied to metaplot after discussions with staff) to which OOC response was somewhat lukewarm - it's as if as long as it doesn't involve apocalyptic-level events that can wipe civilization if they aren't stopped it's not worth their time.
This is a pretty hard issue to solve. I don't know that it can happen on the ST level. If constant escalation is the only way to keep things interesting that's a dead end plot-wise.
The other thing is... it's no secret Arx has an emerging dino issue since people - especially ones present in alpha - have a crapton of XPs and gear, but public scenes even now consist very clearly of the haves and have nots. The same challenge ("climb a wall") is barely made or failed by some while others score as much as three times the necessary difficulty they need to achieve it. This effect is only going to become more prominent and it will increasingly turn newbies and casual players irrelevant; it's disheartening to play a healer when the person next to you is a better healer but also a superb swordsman and expert politician who's also a High Lord with a glowing sword that talks and solves crossword puzzles.
Overall the activity level is so high things continue to be fun, but I'm curious to see if others have ran into similar challenges. Perhaps this is just what I've encountered so far and it's more anecdotal than I think it is. For the time being what I'll do is limit the scope of upcoming PrPs and aim them at smaller, more focused groups to see if that works better.