To play devil's advocate (not that OP is an devil), you want a CDN serving up static assets anyway, and maybe take care of SSL termination and security depending on your sensitivity needs; haproxy is great for load balancing and centralized logging; vulcand to handle reverse-proxying; and at that point, all you're left with is compression, which a reasonable web server should be able handle. Now you've got a suite of specialized tools that will do their jobs well, and you probably have most of them in your stack anyway.

Granted, it's more complexity, but nginx certainly isn't the must-have that it used to be.