This is a cool way to use pf to cut out intermediate daemons, but you are losing some of the benefits of that setup. For example if you have nginx or lighttpd do the load balancing you can also have that server serve some static content for you. I have my rails apps setup so that lighty will serve css/js/jpg/png/etc as it is significantly faster than Mongrel serving those files.

If you are using a CDN or simply don’t want that setup of course you’ll need a setup something like this.