I haven't used it, but can't think of any reason why it wouldn't work.
Nutritionally, the stuff is practically equivalent to high fructose corn syrup in the way it's produced and the way it is metabolized, so it will certainly ferment.
Not sure what the flavor contribution would be in a beer. The only fermented agave I've ever consumed was in the form of tequila...I certainly like that stuff...but I'm guessing that in a beer it is more in the category of an adjunct ingredient so the flavor contribution would likely be more subtle. But again, I'm just guessing here.
Opinions will abound, I'm sure...probably best to just do a batch and report back...it's the only way you'll know for sure if you like it.