I actually wouldn't compete with those servers, because they are very language specific. I'm aiming for Mongrel2 to unify all the languages in the network arch

I actually wouldn't compete with those servers, because they are very language specific. I'm aiming for Mongrel2 to unify all the languages in the network architecture so that you can do what companies actually do: use what works. I could easily see Passenger or others providing a 0mq connector that Mongrel2 can talk to. Passenger is bad ass at running Ruby, so no point in trying to do that better.