I learned Smalltalk in the Elder Days (1985). Coming from C and Pascal, the power and majesty of true collections—dynamic lists! that you didn't have to build yourself with pointers! sets! dictionaries! iteration over objects not integers! selection, rejection, injection!—was astounding. The ability to define behaviors in a generic not intensely specific way, the ability to meta-program, the ability to twiddle your environment directly—just so many world-changing innovations. Thankfully most of these advances are now baked into Ruby, Python, JavaScript, etc. (either right into the language, or with ready-to-hand libraries like itertools, more-itertools, and Underscore.js).

The image—all your code, data/state, your entire OS and windowing system, your IDE, all rolled up into one—that was an interesting approach but honestly that is the worst thing about Smalltalk. No modularity. No version control. Your image persists your data and changes forever—including any mistakes you make, knocking around inside big ball of ever-declining clarity and reliability. Over time every image collects entropy, mistakes, and bitrot like no one's business! Eventually it gets to be impossible to figure out how to fix it, or takes so much energy to maintain you won't bother. Then you have to chuck it and start afresh. Rinse and repeat! Give me today's alternative, non-persistent dev environments and version control, any day.