I've used eco complete, flourite, regular gravel, and tried an experiment with sand, and found that the eco complete did the best job of holding, and promoted the best root growth. the flourite is too light, like flaked stone. the eco complete is like dritty big soil almost. smaller than regular gravel... I set up a tank for a friend with filter sand, and it seemed like a nice material. it was heavy and large compared to most sand I've handled. I could see sand working with some things, but being a pain for others. I think it depends what you want to grow.
I also noticed bags and bags of a new aquatic garden soil at lowes. I believe it was made by scott. it was cheap. I didn't get any though.