RGT Cycling is working out pretty well, the iOS controller app on my phone seems to crash/freeze on pretty much every ride when I wake up my phone to end the ride but recovers the data when I restart. The RGT Screen app on my Windows laptop is stable and looks great.
Not too many riders, but plenty of NPC riders around to keep it lively. Like I said before, this is just some visual distraction for my TrainerRoad workouts so I don't really care that it's missing all the social Zwift stuff. I don't think Zwift is that great for structured training, to be honest - I always get caught up going for PRs or racing other riders.