I would argue design complexity and usability are proportional. Regarless of what dictionary.com has to say. Less complex systems would be inherently less usable and systems "quick to recover from errors" would be more complex and therefore more costly.
I'm not sure what you are on about... which system is more usable, a Mac or a Cray? Now, which system is more complicated?

The same can be said for many things... tax law for example... would a simpler law be more usable? Which recovers from errors more easily, simple modular code or complicated spaghetti code?

cheers,

catch