If you ever want to take a look at a simple JME game that uses an ES then you can take a look at my Asteroid Panic game. It uses Zay-ES which it the entity-component library I wrote that works with JME (though not much JME specific) and also optionally has persistence and networking.
Example here:
The architecture works even for simple games and I use it all the time now. I have trouble thinking any other way anymore, re: games.