APL isn't all that weird once you spend a little time with it. It's "just" a dynamically typed collection-oriented language. I think people look at some screenshots, make a stupid joke since they aren't familiar with the notation, and move on rather than digging in. I highly recommend Dyalog's dialect for a comfortable IDE, OO support, .NET support for GUIs on Windows etc.

For MS' APL dialect, you can get the whole thing from: http://www.aplusdev.org/

My understanding is that they still have many many lines of code written in this language running. They also use a commercial intellectual successor of this language called q from kx systems. Many other firms do as well, but I won't name them since I don't know which ones are public about it.

I'm pretty sure that the firms I know creating new languages are not public about it, but there are at least 3 very very large ones doing so. Aiming for a functional flavor, large-scale parallelism, streaming, low-latency processing of large data sets, high-quality compilation and leveraging new hardware are common themes.