the shultz aquatic plant soil, and clay soil conditioner are the same thing - both 100% arcilite (at least, last time I checked)
It's the good ole add "aquatic" to the name = double the price!
I've got two tanks set up running CSC - very nice. Yes, very dusty, even after much rinsing, and it IS very light, so be careful vacuuming or else you can just suck up a siphon-full of the stuff!
That said, the plants love it - lots of roots, and whenever I pull anything up, lots of roots are clinging to grains of the stuff.
I find it easy enough to plant things in - the grain size is small enough that it holds well untill the plant gets rooted unless you have a big fish that knocks things loose (like my Bichir).
Overall, I'm very happy - 40# for next-to-nothing at wal mart is an absolute steal! Anyone with more money might consider Flourite or Onyx, but for us on a budget, it's perfect.