[defunkt]

If each Unicorn worker listened on a different port, we'd have to use one of nginx's load balancing strategies (unless I'm misreading your comment).

We have not had success with them in the past which is why we employed HAProxy with mongrel.

[blasdel]

You read me correctly, I don't see why load balancing should be taking place down at the app server level.

Aren't you going to have multiple machines each with their own blessing of unicorns? You're still going to have to use some kind of load balancer in front of independent sockets.