Being an Amiga fan, I have a fondness for the Rexx language. On that platform, almost every significant program supported ARexx, allowing a high degree of interoperability and customability. So when PCDOS 7 added Rexx (after dropping MS Basic with v6), I expected good things.
... But I don't know of any. Was it just too late in DOS' lifetime for folks to take advantage of this powerful tool? Or was it inferior in some way that would not allow the benefits ARexx offered Amiga programs? I know a major feature offered on the Amiga was "ARexx ports", which were actually native AmigaOS IPC channels which ARexx made simple to use.