What kind of alternative sugars are you thinking of? Dextrose is what is usually recommended, but I have been using table sugar for years with great results. I have also used DME with good results, though I did find it took longer for the beer to carbonate with it. I have tasted beers primed with honey, molasses and maple syrup, they all work, the (not too) difficult part is figuring out the amount to use.
I honestly couldn't tell maple syrup had been used to prime the beer I tried. As RPh Guy said, the amount is too small to really add some flavour, although molasses in an English Ale can add a bit of flavour.