Hi Reid,
Java moss grows well in a low light environment where most other freshwater plants would perish. It also does well under a variety of temperatures and water conditions, even growing above the water line on a suitable substrate. In addition, it's bushy consistency serves as a good cover for many aquatic animals, especially fry, larvae, and the many minute organisms on which they feed (in a healthy aquarium). It also spreads well and often has to be thinned out.
Chip