Just had the first half of that bottle of Art of Darkness. Very very good, reminds me strongly of Trois Pistoles and Maudite. You could say flavor-wise it's a lovechild of sorts, even though it's an Ommegang brew not Unibroue. It's a limited release, one time each year, but if your lucky enough to find it, grab it.
Don't hesitate, don't think it over, just grab it.