I agree with Tsunami that it is quite light and can difficult to work with in totally submersed applications. Combine this with the fact that I use MTS in my tanks and well, it is tough to get things rooted initially.
For that reason I have been experimenting with a 50/50 Schultz/Flourite mix. The flourite gives the substrate some added weight and the Schultz gives it some added cheap
Additionally, they're similar in color and size, so I don't feel like it comes off like a mix of media.
Just my 2 cents.