When NGINX showed up it beat the then dominant apache on resource utilzation hands-down.

It's also very configurable and has a lot of modules, both in-house and third party.

The only downside for me: as of late the whole commercial part of the project has been gobbling up everything to shove the non-free version to the point where it's hard to find info on the free version, e.g., the wiki page that lists all the third-party modules. The nginxtutorials site seems to be a good resource.

Btw one of the main devs forked it into freenginx:

Dounin writes in his announcement that "new non-technical management" at F5 "recently decided that they know better how to run open source projects. In particular, they decided to interfere with security policy nginx uses for years, ignoring both the policy and developers' position." While it was "quite understandable," given their ownership, Dounin wrote that it means he was "no longer able to control which changes are made in nginx," hence his departure and fork.

Also, fun fact: this is probably the only instance of russian software muricans don't cry Commie! all the time (maybe because the parent company was acquired).