Yeah, you could compare it to eating a bunch of ginger in terms of intensity. The effect is not like ginger though.
The effects are only so mild to be confused with placebo if you are not used to working with plant spirits. Chewing a root for it's spiritual value is a very different practice than chewing a tab of acid for it's hallucinogenic value. It's a relationship developed over time between you and the plant. "Plant Spirit Medicine" by Eliot Cowan is a good book to check out if you are interested in this sort of thing. I highly recommend it.
Regarding "teacher" plants: When working with plant spirits over time, sitting in meditation with them, some plants moreso than others will help you understand life. Tobacco is the best example I can give. If one works with the spirit of tobacco, giving gratitude and following through with any tasks the plant spirit may ask of one, one can sit in meditation with the tobacco spirit and receive wisdom. Maybe you will learn a lesson about how to treat other people, or about how to take care of your body, or how to properly show gratitude to a particular spirit, or what the next step on your path is.
It's sort of hard to explain how these things work. For example, stones can be teachers. You don't even ingest the stone or crystal, you are just sitting with it or perhaps near it in the case of a boulder. If one can slow down enough and tune into the right frequency, communication with just about any part of Pachamama is possible. We just forgot how to do this as human beings. It's something that humans have always done in the past, one just has to practice and remember.
It's not the effects that teach you a lesson, it's the spirit of the plant. One could receive the lesson without even ingesting the calamus, by sitting with the live plant in the wild. Give the plant an offering of something that is important to both you and the plant and ask for guidance and sit in meditation.
If I could find the American variant, I would order that personally. It's said to have a better flavor and effect, but as I said I never got around to trying any, mine was always just the presumably Indian stuff (they grow most of the calamus on the consumer market) bought from a local herb store. I haven't even seen a source to buy fresh root online but it's probably out there. Calamus grows wild in the US still, I'm not sure what region you are in but I believe it grows throughout the midwest. I think the best would be finding the plant and harvesting yourself.
Here's an article that will clear things up for you. It's really good and worth reading the whole thing.
http://www.herbcraft.org/calamus.html
PM me if you have further questions about herbs or working with plant spirits, etc.