Dense Oxygen/Nitrogen atmosphere.  Specific gravity within 1.1 to 1.8 Earth
normal.  Random and occasional violent weather current patterns, with temps
ranging from 20 to 50 degrees Celsius.  No land mass to speak of, making
mining for Ore more difficult.  Organics production quite good, (one of the
best) but a poor environment for building Equipment.  Class O planets are
more challenging to habitate, but are almost as safe as class M.  Good
population growth curve and decent population harmony.  Their entire surface
is habitable with proper gear with the only drawbacks being the costs to
settle and build citadels.