snail-eating plants

Little has been written about the effect of snails in planted aquariums, until the past few days. I too agree that chemical eradication should be a last resort. I also wonder how many poople consider snails to be a problem. I have a 20 gal. planted aquarium with many (80-100) snails (I believe they are ramshorn) and they cause no harm to plants or fish. What exactly do snails do in a planted tank (are they scavengers?) and are they a cause for concern or intervention? It seems to me they are harmless.