For a variety of reasons I recently needed a reverse proxy(#1) and went with Apache 2.2 w/Google's mod_spdy. What are the advantages, if any (above and beyond that nginx has a lot of cred right now), of using nginx? In a prior build-out nginx didn't even support HTTP/1.1 on the inside side of the reverse proxy, while Apache 2.2 does.
#1 - We use it as a "least effort" geodistributed CDN. GeoDNS directs worldwide users (a small number of very high value users) to their local reverse proxy that has local caching of cacheable resources. Those proxies speak to the normal HTTP back-end servers through an SSH tunnel).