I was born in the late 1980s and thus was too young to experience NeXT in its heyday, but sometime in high school was when I learned Mac OS X and its NeXT heritage. I was enamored by a highly usable Unix GUI, and since then I've been a fan of Mac OS X and NeXTSTEP. I even own a non-working NeXTstation Turbo Color that I bought on eBay with the intention of restoring it.

However, I was so intrigued with NeXTSTEP as Unix with a polished GUI that I didn't realize or appreciate its Smalltalk influences until roughly a year or so ago. In a way, NeXTSTEP could be thought of as the realization of a polished Smalltalk desktop, albeit with Objective-C and Unix rather than actual Smalltalk. On one hand, NeXT lacks Smalltalk's image-based, live-object environment, which I think is something that would still be revolutionary if a desktop operating system environment offered this today. (My dream is a desktop based on live objects, but the substrate I'd personally pick would be the Common Lisp Object System with its support for multiple dispatch.) On the other hand, Objective-C brought the benefits of Smalltalk-style message-passing object-oriented programming to NeXTSTEP programmers while being compatible with C, which was important for supporting an ever-growing base of software written in C. NeXTSTEP also sweetened GUI programming through its Interface Builder, which was originally for Lisp.

On a somewhat related note, there were attempts by Apple to catch up to NeXT or to even leapfrog them. The Pink/Taligent project would have created a modern operating system (e.g., one with preemptive multitasking and memory protection) with an object-oriented API, though that API was in C++ instead of something more dynamic such as Smalltalk, CLOS, or Dylan (Apple's own internal language that was heavily Lisp-influenced but had an Algol-like syntax). Unfortunately this project failed, which led to a scaled-down effort called Copland (the original plans for Mac OS 8) which also failed, which ultimately led to the purchase of NeXT and the return of Steve Jobs.