Is it really different enough that it crosses the threshold of being worth using?
I find that hard to imagine. How much time do you spend looking at archived boards? What would you do with two lists in a column that you can't do today with one list that has some "subtitle" cards?
I'm asking because I'm genuinely curious to know use cases like that, not rhetorically.
My own problem with Trello (that I use a lot despite that problem) is that I feel the need for more than one view of my data, i.e. sorting it in more than one dimension. Perhaps having the ability to have two boards with the same cards. Unfortunately, I cannot imagine any good UI for this.