By chance, I got to use a Xerox Star for the first time recently. It was in a room with a Lisa and an early Mac. The speed differences were real, but it could be that my familiarity with the Mac accounts for the feeling of clumsiness with the Star and Lisa. Of course, he might well be correct when speaking from a programmer's point of view. However, I've always been more concerned with users.
Programmers do their work but once, while users are saddled with it ever thereafter.
I find looking at the past not nearly as interesting as looking into the future. As Horn says, and as I have written in a number of articles, things haven't changed as much as the hype would have it. The future lies with getting rid of the cumbersome and complex systems we have now and moving to simpler, more direct methods of harnessing the power of the processor.