It also should be noted that Oberon's UI (which you can try out by downloading the emulator from here[0]) might be an initial culture shock if you are used to a Windows-like interface, but when you learn how it works it actually is both very powerful and very consistent - which helps into usability since everything works the same way.

AFAIK Oberon was actually used by "regular people" at ETH Zurich for a long time.

(and a lot of people ran and still run their programs maximized anyway)

[0] http://www.projectoberon.com/