My primary exposure to Lua is as an embedded scripting language (at work), although it does look like it would be useful as a stand-alone language. I had a friend who was heavy into that about 10 years ago.
However, for a stand-along language for one-off utilities, my default tool of choice is Python. Perhaps the reason a lot of folks aren't interested in Lua as a general-purpose language is the existence of languages like Python, Perl, or even PHP (which I use under duress, but others seem to like).
