With Rails 4 and Ruby 2.0, is it still necessary to install Phusion Passenger? It is my understanding that the purpose of Passenger was to manage memory leaks which were present before Ruby 2. If this was not the purpose of Phusion Passenger, please elaborate!
Well, personally, I recommend strongly to use Unicorn + Nginx over Passenger. Consume less memory, more efficient.
I use it personally with RedMine.
Phusion Passenger or Nginx+unicorn setups are needed only in production environments.
I find Phusion more solid for single applications on single VMs even if it consumes more memory. Version 4 enterprise edition added some advanced featurese, like rolling restarts.
Instead, I find more suitable Unicorn for a shared hosting configuration.