When I worked at Telstra in the 1990s, part of the team building WorldFax, all that work was done on OS/2. I programmed for OS/2. It wasn't bad, I got used to using it. It isn't anything I would joyously go back to.
But it appears that many people have clung to OS/2. Apparently it's still in use in many places. Companies are stuck using it because there's no upgrade path for their software. There's an annual convention called Warpstock. There's a website and a company called Arca Noae that supports old installations of OS, and they have licensed from IBM and they are going to release a new version of OS/2 codenamed Blue Lion.
Last week, there was a news item about a French airport that had to shutdown because they had a glitch in their Windows 3.1 systems. After reading the news items about OS/2, I have to believe that the French airport is not alone. There must be a lot of places that are stuck on old systems without an easy upgrade path. Maybe somewhere out there, there is a bank that does its payroll with an ancient CP/M system. I would not be at all surprised.