I finally got around to trying St. Bernardus Abt 12, a Belgian quad that many people say is as good as Westvleteren 12, the ellusive, so-called best beer in the world. I can't comment on Westy 12, I've never had it. But I liked Abt 12 a lot, and thought it was like a very slightly dryer Rohefort 10.
Abt 12 is a dark brown with copper highlights, and about two fingers of heads that fades but leaves thick sheets of lace. The aroma is complex; dense, dry, rich, fruity. The flavor is slightly sweet up front and dry and very crisp in the finish, and in between there are different notes with every sip. Citrus and bananas, toffee, chocolate, caramel, walnuts, coffee... and then, on the exhale, other combinations of those flavors present. Abt 12 is delicious, and it's a little more affordable than Rochefort 10. Without a doubt I'll have it again.