I have to agree with Denny. My buddy makes a great Maple Brown Ale and uses maple extract. His beer reminds me of eating pancakes in liquid form.Yuck! (For me that is,its a matter of opinion) To me maple is a flavor in beer that should be an accent, not the main flavor. I think the dryness that adding a bunch of sugar in the form of maple syrup could work ok with a beer that otherwise would be sweetish. Ironically maple syrup would make a beer less sweet. I am yet to find one that's perfect.
It's not the main flavor and is more of an accent, but you can taste it. It's mainly a malty brown ale. I think a sweet maple syrupy beer would be gross too.