There was a bunch of advanced things in Genera: the error handling system (-> Condition System), Flavors, CLOS, an object-oriented generic networking substrate, an ephemeral garbage collector (which vastly improved the usability of a machine with large virtual memory), support for embedding the OS into other hardware / OS combinations (like a Mac or a SUN), support for programing in C/Pascal/Fortran/Ada with a language sensitive IDE, support for color/video/3d/..., versioned source code management for files, ... Important also and mostly unique: things like the error handling system and the presentation-based UIMS was widely used in the operating system and the applications. When did you last see an operating system which was using something like the condition system (with integrated debugger and restarts) as its main error handling and gives that to the end-user? When was your TCP/IP stack written in Flavors/CLOS and could be debugged/extended on the fly? There was also a version of Genera, called Minima, that ran on embedded Lisp Machine boards.