I just bought some but haven't got it in yet. I'm setting up a 20gallon long for multies next week and plan on using it for that. The 'Reviews' section at this site seems to think well of it though folks comment that it's not as dark as the pictures show. I'm considering adding a couple 5lb bags of straight black non-active sand to it.
I have carib sea products in all my tanks, and I'm very happy with them, but I will say If you are getting one of the gravel products (as opposed to sand) make sure you see it in person because they don't all look like the pictures on the website. Some of them are mostly crushed shells, not really gravel at all