I've used it in production at multi-national organizations.
In fact that's how I learned to code. 10 years ago I was a business analyst who couldn't get the dev group to work on my projects in a timely fashion. The ability to use arc was in reach for me, even though I had no programming experience at all.
I actually wrote and released 2 internal apps and 1 external app that had good use (a few hundred users using it daily/weekly to get their jobs done). This was in production for a few years until I left in 2012. I'm pretty sure they're not using these apps anymore.
> What sorts of systems would it excel in and what sorts would it be unsuitable for?
I think its primary strength is the short learning curve. I also I think it's unsuitable for anything which needs to use existing db connections. Even though I did hacks to make that work it's the primary reason my apps could not be adopted by the dev group.
> What could be done to alleviate for Arc’s lack of features?
* better db integration
Or if there's no interest in db integration then make it focused on compiling to js for mobile devices where db integration is less of an issue.
edit:
> In fact that's how I learned to code. 10 years ago...
It's kind of ironic my first post was about a most recent topic[1]:
"After playing for a bit I noticed my "set x" functions were
clobbering each other...so I started converting all my function to use
"let" statements."
"why wouldn't the ARChitects of LISP or ARC make a set like
function that is global within a function ?
Also, It's really embarrassing reading my old noobish questions/comments. I think we need to take this forum down and start a new one to preserve any sense of pride I could possibly have. :)
Regarding db integration, I recently read a bit on Jarc (arc on Java - http://jarc.sourceforge.net/), and the author specifically added in that ability.