I like the look very much and the readability of the code as well. Major problem for me is that it only works on firefox. Chrome support seems to be not working due mainly to the way the button colors are drawn (i say no support because it does not look correct, maybe 80% of the way there).
Also, the "card actions" section at the bottom of each section are hidden. This means you can't share items or mark unread or any option that is supposed to be there. I'd like to see this added back if possible.
Great script, keep it going!