The first time I remember Rexx being mentioned was when I installed OS/2 2.0.
The installation procedure asked me if I wanted to install RexxUtil, an extension to Rexx.
Since I didn't have the slightest idea what Rexx was supposed to be doing on my system with its limited hard disk space, I answered NO.
Soon after that I bought VX-REXX, to try some programming in OS/2.
Though one can make nice interfaces in VX-REXX without any knowledge of Rexx itself, I soon found out I needed to know more about Rexx if I wanted to do some "serious programming".
That's when I heard about Dick Goran's OS/2 Warp Rexx Reference Summary Handbook.
Since then, I have spent many days and nights programming in Rexx.
One of my projects involved controlling an HP ScanJet 4c over a LAN Server based wide area network, which was, I suppose, the limit of Rexx's possibilities as far as maintainability is concerned (though I bet that many Rexx programmers won't agree).
Another project involved Microsoft Windows NT 4 Terminal Server with Citrix MetaFrame and Load Balancing. In short, this enables OS/2 users at the office to run a full NT 4 desktop in a window on top of their OS/2 desktop (will work in Unix and DOS too, with the appropriate client software).
With 4 IBM Model 325 Dual Pentium II servers, each configured with 512 MB of RAM, you'll hardly notice a performance difference compared to a locally installed Windows NT 4 Workstation <g>.
I wrote some administrative tools, both Regina Rexx scripts and batch files (called "shell scripts" in NT), for NT 4 TS domains.