At first Lua seems strange, but after a while you start to appreciate it. It’s designed with a small number of concepts that manage to lead to expressive code with excellent performance.

I use it for two things: scripting TeX¹, where it allows you to do amazing things², even complex numerical calculations³ within the document; and writing Pandoc filters, where it is now the standard method.

1 ‘LuaTeX comes of age’. LWN. Available from: https://lwn.net/Articles/731581/

2 http://wiki.luatex.org/index.php/TeX_without_TeX

3 http://www.unirioja.es/cu/jvarona/downloads/numerical-method...

I was a huge Lua fan, but once I jumped on the typescript bandwagon I found the lack of (production ready) desugaring and static type compilers for Lua to be a negative. The language is fantastic, but what I expect from a scripting language is always expanding, I guess