Is Satori the same as Enlightenment? Is the Zen term Satori the same as enlightenment or does it have different nuances or emphasis over what is commonly meant by enlightenment in non-Zen texts. If it is the same then why is used at all. Is its usage just a cultural thing and enlightenment could equally be substituted?
No, satori is not complete enlightenment, it is an a-ha moment when the practitioner finally realizes "how things are":


  Seeing his own original nature, he discovers that the ground of this
  nature is innately free of defilement, and that he himself is
  originally endowed with the non‐outflow wisdom‐nature which is not a
  hair's breadth different from that of all the Buddhas.


From this moment on, one's practice stops being guesswork or imitation and becomes informed by real understanding. In Zen this is known as "sudden awakening, gradual cultivation":


  Although he has awakened to the fact that his original nature is no
  different from that of the Buddhas, the beginningless habit‐energies
  are extremely difficult to remove suddenly and so he must continue to
  cultivate while relying on this awakening. Through this gradual
  permeation, his endeavors reach completion. He constantly nurtures the
  sacred embryo, and after a long time he becomes a saint. Hence it is
  called gradual cultivation.  This process can be compared to the
  maturation of a child. From the day of its birth, a baby is endowed
  with all the sense organs just like everyone else, but its strength is
  not yet fully developed. It is only after many months and years that
  it will finally become an adult. (from Secrets on Cultivating the Mind  by Bojo Jinul)


Chogyam Trungpa also speaks about it:


  Having received transmission and having had some kind of realization,
  you have to follow it up; you have to become liberated. Some people
  think realization is liberation, but in our case, it is not. When you
  realize something, you have to practice that realization, and then you
  are liberated. So realization does not mean you are liberated; it
  means that you have just touched on the possibility of liberation. Realization is like seeing the first rays of sunshine on the horizon -- you know that the sun is in the sky.