Their main breaking point with the Big Ls is the argument that land ownership itself is a government monopoly: the system we've got today is not based on the Libertarian principle that one has a right to the fruits of one's own labor, but on a holdover from the days of monarchy -- a small group of powerful people is given sanction to extract payment from those actually putting labor into the land they "own." Someone who's born owning eight million acres and who sits back and earns a fortune their whole life from renting it out might not be entitled to that free ride! Imagine that!
This doesn't have a tremendous bearing on income inequality, but I thought I'd point it out as a note of side interest. It's certainly a step in the right direction for Libertarian thinking, and does address one of its major blind spots.