Combine all of the ingredients in a blender, and blend until very smooth. Taste and adjust the flavor to your taste, adding more vinegar for a tangy flavor, or more maple syrup if you want it a little sweeter.
You can serve this dressing right away, or store it in an airtight container in the fridge for up to 5 days. (I think the flavor is the very best within the first 48 hours, if you plan on making this for company!)
You can use honey instead of maple syrup for sweetness. In that case, you might want to use only 1 to 1.5 tablespoons, since honey is sweeter than maple syrup.