The $|++ idiom will turn buffering off for when we want to see our output, and we want to see it now!

... thus giving the illusion of better performance at the expense of better performance.

Sometimes that's necessary. I see a lot of programs that disable buffering out of habit where it's unnecessary. Buffering's done for a reason — if you really don't need it, that's one thing, but I think it's silly to disable good things.