Kanban boards have existed since the 50s. The "magic" of trello was the instant updates. It was a perfect example of software eating the world.
You can talk to it from just about everywhere including the terminal, that's a big reason I use it, it acts as a clearing house for all my stuff, I even use a chrome plugin to store "bookmarks" to stuff I've clipped.
E.g. being able to make layout changes(have lists that span columns for example, or cards that show more of their information on the cover). Or more flexibility in colour changes/background, or ability to style cards.