But not so fast that that alone made me switch. What made me switch was that Lisp machines (both Symbolics and LMI) were so gratuitously, baroquely complex. The manuals filled a whole shelf. Each component of the software was written as if it had to have every possible feature. The hackers who wrote it were the smartest and most energetic around. But there was no Steve Jobs to tell them "No, this is too complex." So the guy in charge of writing the pretty-printer, for example, would decide. "This is going to be the most powerful pretty-printer ever written. It's going to be able to do everything!"
I learned how to program a Symbolics myself, from reading the manuals. I sometimes suspected that I was the only person who'd ever done this-- that everyone else who knew how to use the damn things had either learned how from the guys who invented them, or had learned from someone else who had. The libraries were so hairy that I generally found it was faster to write something myself than find and understand the documentation for the built-in way of doing it.
Unfortunately this complexity persists in Common Lisp, which was pretty much copied directly from ZetaLisp. In fact, both of the worst flaws in CL are due to its origins on Lisp machines: both its complexity and the way it's cut off from the OS.