When POSTing an entity using REST, you would expect to get that created entity back (particularly to be able to see computed fields, like the
created fields), but Drupal 8.0.x's REST implementation does not do this. All you get is a
Location header that points to the URL for this entity.
Consequently, in Drupal 8.0.x you first have to POST an entity and then GET it (using the value of the
Location header in the response). This is both painful and slow (2 round trips instead of one).
As of Drupal 8.1.0, Drupal's entity REST responses (
\Drupal\rest\Plugin\rest\resource\EntityResource::post()) returns the created entity.