I have been using nginx since 2010 now, and have grown to love it for a great deal of things.
nginx is not limited to the web; it can also natively load balance TCP/UDP streams amongst other things. I will recommend it for most use-cases. However, if you're currently using Apache and thinking of switching: First determine if you need to and whether you can do it easily (nginx has no .htaccess!).
- Setting a website as default/fallback.
- A safe(r) example of how to configure PHP in nginx.
- When and when not to use permanent redirects.
New to nginx? Read the nginx primer by Martin Fjordvald (external link).
I have been using Apache (later "Apache HTTP Server") since 1997. So probably for around 20 years now.
Even though I love nginx more, Apache still has some qualities that can't very simply be moved to nginx (.htaccess is unique to Apache)... especially when you're doing shared hosting for a lot of customers with each their own wishes.