I've always been fascinated with NeXTSTEP. It's kind of unfortunate that even the basic interoperability features that made it over to Mac OS, like Services, seem underutilized. I often forget they even exist, because they don't seem core to the default workflow.

I installed OpenStep in a virtual machine after reading this comment. I poked around a bit, but I'm not sure I encountered any of the sort of stuff you're talking about in the OS. Do you have any examples of things I could try to experience some of the magic?