Can anybody tell me if the skill points actually have a use? I love them clocking up, but if there's nothing to spend them on or to use to unlock what is the point behind them?
They have no real use but only give you a gamelike experience to better motivate you. Judging from discussions by people who are annoyed by not getting points for this and that, they clearly have some value as they keep us addictive to learning languages!
I believe all they do is show yourself off, and give you a perspective about what you've done recently/over your lifetime on duo-lingo. Nothing great, just something shiny to hold over people you know if you're learning with them I suppose.