Drupal 7 Entities
While looking at some of the differences between nodes and entities, I came across this interesting article explaining what entities are and when should one use them. It served as a good corollary to the existing documentation available on drupal.org about entities.
http://www.istos.it/blog/drupal/drupal-entities-part-1-moving-beyond-nodes
http://www.istos.it/blog/drupal-entities/drupal-entities-part-2-what-where-and-when-entities
One of the major advantages custom entities have over a node, is that, if there is a field inherently associated with that custom entity, and one would like to load that field data in just one query (may be performance reasons), it makes sense to store the field data along with the entity in the same row instead of having to query 2 tables, 1 for the entity and the 2nd for the field data
