I've used Hydrophyte's GroSoil and GroHumate tabs for two different setups over the past year or so, and I've gotten some pretty remarkable changes in my tanks. The growth and health of all my plants really perked up, even though I was dosing EI, using pressurized CO2, had superior lighting, and a "plant" substrate. The colors, especially for my red plants and cryptocornes really started popping too. I swear by them! I add more about every six months, and it really has paid off for me.
As Barbgirl mentioned, there is a LITTLE dust that comes up if you yank out rooted plants, but it isn't much more than what you would expect by simply removing rooted plants from a substrate without the Gro Tabs. From my experience, the "dust" is quick to settle or is simply filtered out. I've never found it problematic by any means. Certainly, the benefits by far outweigh any sort of very temporary "cloud" that may arise.
One of the best products for planted tanks out there, in my opinion.