I started thinking about mead and the process of turning honey, water and yeast into a delicious alcoholic beverage. Then a thought crossed my mind. If you could turn what's basically sugary honey water into alcohol, couldn't you do the same thing, but instead of using honey, you used real maple syrup?
A guy in our local HB club taps his own maple trees and uses the sap as brewing liquor for what he calls a "maple wine." It's quite good, but it's not a true mead. I keep telling him to throw a cup or so of honey into it so he can enter it in competition as a specialty mead.
I've brewed with maple sugar a few times, but only to make beer. The maple character is relatively delicate, so you're better off using lower grade maple syrup (paradoxically, Grade B maple syrup has more maple flavor and aroma than the "better" stuff). I've never done it, but I'd imagine that you could get nice maple notes if you used it as a priming sugar.
Unless you're tapping your own trees, given the expense of maple syrup, I'd do a mead using mostly neutral-flavored honey, then "feed" the fermentation with maple syrup so that the maple dominates flavor and aroma.
Finally, only use pure maple sugar. Artificial maple sugar has a base of corn syrup, which produces "cidery" notes when fermented. Artificial maple flavorings tend to be one-dimensional. If you want to create "maple-like" flavors and aromas, add fenugreek seeds instead - they're used to make artificial maple.