> When does widespread ’70s/’80s computing stop being impressive?

When the majority adopts it, or at least knows about it.

> You say “unknown” as if we were talking about some research software, or some old and largely forgotten software. Unix shell programming doesn’t have hipster cred.

It's unknown to those that are only experienced in working in a GUI, which I believe is still the majority of developers. In my experience, anyone of those people are always impressed when seeing me work in my screen filled with terminals, so it does seem to have some "hipster cred". :)

> When does widespread ’70s/’80s computing stop being impressive? You say “unknown” as if we were talking about some research software, or some old and largely forgotten software.

That's precisely what I'm talking about. The 70s/80s produced tons of insight into computer use in general, and programming in particular, that were mostly forgotten, and are slowly being rediscovered, or reinvented every couple years. Unix in fact was a step backwards in terms of capabilities exposed to users; it won because of economics.

It's much slower, and doesn't lend itself as well for building the program up from small, independently tested and refined pieces. The speed of that feedback loop really matters - the slower it is, the larger chunks you'll be writing before testing. I currently believe the popularity of TDD is primarily a symptom of not having a decent REPL (though REPL doesn't replace unit tests, especially in terms of regression testing).

BTW. there's another nice feature of Lisp-style interactive development - you're mutating a living program. You can change the data or define and redefine functions and classes as the program is executing them, without pausing the program. The other end of your REPL essentially becomes a small OS. This matters less when you're building a terminal utility, but it's useful for server and GUI software, and leads to wonders like this:

https://www.youtube.com/watch?v=gj5IzggEWKE

It's a different way of approaching programming, and I encourage everyone to try it out.