Yeah. We load balance across 5 Apache/Passengers and I do rolling deploys (all in Capistrano) by removing a Passenger from load balancing, updating the app, restarting Apache, and adding it back into load balancing with a 10 second delay between each. We tried the Passenger touch restart.txt and that didn't go well at all when we were under load.

Also, if you're using Monit to watch the memory bloat of your passenger processes, when you kill one process it tends to do the same stalling thing on all your processes until the ONE you killed is back up.