I use the root tabs from aquariumplants.com and they seem fine. But what I really like is their applicator tool - you stick it in the substrate and push to have the tab ejected out the bottom. It solves the problem of putting root tabs down without breaking them up, squashing them with tweezers, having them come loose, or disturbing the plants!
"The fewer our wants, the nearer we resemble the gods." — Socrates