As far as performance, the Alto team described the performance of Smalltalk as between "majestic" and "glacial". From my experience with the Alto, Smalltalk seemed unusably slow, and I'm amazed that they could actually accomplish anything with it.
That level of performance was only achieved by PCs when we got 50MHz 486 (for purely interpreted Smalltalk-80 virtual machines, with JITs much slower computers could match the Dorado).