I think most people would say that shallots are a cross between onions and garlic....in flavour. I do know that they are very high in sugars just based on my experience cooking with them. I really can't eat raw garlic anymore, though I wish I could. Shallots are a good substitute for most recipes...more or less.

Shallots are very useful combined with fruit in sweeter dishes. My favorite way to use shallots is in cranberry chutney. They would probably be considered milder, but I would say more accurately that they are less acrid.