How so? I've been using Passenger on my dev machine for over a year now. The original reason I installed Passenger on my dev machine was exactly because of how easy it was to get SSL and subdomains working; the app I was working on at the time had 100% SSL user logins, each routed to their own subdomains.

You're using it with Apache or Nginx though, right? Or were you able to get them working with Passenger Standalone?

Ah yes, you are correct, with Apache.