If you’re interested in using an ES on indie projects, and you’re craving concrete examples, you might want to look at the comments (page 1 and page 2) on Mythruna:
“Since this is a developers forum, I’ll describe a little bit about what went on behind the scenes.
During the early development for this phase, I read about an architectural pattern called an entity system.
…
I had (pre Entity Systems) a plan for how I was going to store the placement of objects in the world but this past weekend when I actually got to implementing it, I couldn’t make that original plan work and came to the point where I needed to solve the general problem of world state storage. This is the kind of thing that Entity Systems make relatively straight forward… and by Saturday, Mythruna had an embedded SQL database that autogenerates tables based on the components stored. (HyperSQLdb for the win.)So at some point I swapped out the in-memory version of the entity system with the SQL version… and suddenly objects were persistent. It was so easy I had to double check a few different ways that it was actually working. :)”
…but of course, also: use the Entity Systems wiki – put your questions there, put your ideas there, and (most of all) if you have an ES project or ES source code you want to share, please add it to the wiki!