We primarily use Mingle for project management at Braintree. Personally, I find that the Mingle card wall wastes too much space. Each card is the same size, so short cards are filled with empty space. I prefer a denser view, so I made a Greasemonkey script which changes the card heights.
It changes the card wall from this:
You can find the code and installation instructions on GitHub: remove_mingle_card_height