How important is the minimum layer height on a 3d printer?
I believe the Slic3r Manual summarizes this quite nicely:


  A thicker layer height will provide more flow, and consequently more heat, making the extrusion adhere to the bed more. It also gives the benefit of giving more tolerance for the levelness of the bed. It is recommended to raise the first layer height to match the diameter of the nozzle, e.g. a first layer height of 0.35mm for a 0.35mm nozzle.


In other words, larger layer heights for the first layer typically gives better adhesion, and makes inaccurate bed leveling (and auto leveling) still work.