Now, in this contrived example, it's pretty obvious to see what's going on and what's being assigned where. Consider, however, extending this to a more complex real-world scenario, involving accessing elements in deep data structures, subroutines to format numbers, regular expressions and the like. Clarity, maintainability and even code elegance are quickly lost, all for the sake of a few keystrokes and a newline, unless the person doing the coding is very careful about how he uses the operator.

Very careful? Is it really that hard to see when if/then/else is going to be less clear than the ternary operator (or vice versa)?

Use whichever one's the clearest in a particular situation. Saying that one or the other is less clear or maintainable without a particular context is just silly :-)