@Mark McWilliams -

I was unclear if this is for only the new "2012" theme, or would affect any well-made theme (and could not view your linked tweet).

But I see in your Trac-link, Koopersmith says:One of the main goals here is to make it easy for plugins and themes to add to the customize controls and preview without having to unbind large portions of core code.

That sounds like this control will be a generic UI element that any theme could be given (or plugin!). Hmm!

Is that correct?