Nor would I, though I have no personal experience with it. Yesterday i happened to see this very fixture over some amphibian tanks in one of my better local stores, and had a discussion with the owner about them. She had a single strip over what was probably a 20g tank, with newts. The light was dim, perfect for the newts, but I couldn't see plants managing, and said as much. You can use two strips, but then you block the entire top of the tank which makes feeding and maintenance awkward. She had some display tanks, nano cubes type, maybe 2-4 gallons with these lights, and the plants (crypts, something else) were doing fine. But of course there is bright store light above them too.
Underh2o mentioned a double bright version, I don't think that was what I saw yesterday.
I know the low wattage is appealing (lowers the electricity use/cost) but if it takes tow 10w to cover the 20g, I would go with two 10w compact fluorescent bulbs in a standard incandescent fixture (as I have over my 10g and 20g tanks) and that is perfect light.