Well, it's strong
strong flavour, strong drunk, and strong hangover. It's very very sweet... there's a reason it's called "The End of the World." I can tell you that you don't really want to drink more than one of those big bottles with the cork in it in a sitting... unless you really don't have anything you have to do the next day. If it's a normal sized bottle... only drink the four pack. It's got about as much alcohol as an eight pack of typical (5% alcohol) Canadian beer.
They've got some other strong beers like that; Don de Dieu (Gift of God), Trois Pistoles (Three Pistols, the name of a small city in Quebec) and Maudite (The Damned).
That firm makes some other great great beers though. I can recommend Eau de Benite, Raftsman, and Blanche de Chambly. Usually Fin du Monde gets introduced into a market first because it's one of the highest alcohol beers in the world, which brings out the "I can take 'cause I'm a /man/" ('je peut le prendre parce que je suis un homme' for those following along at home) drinkers. The strong sales from that then justify introducing other beers from their lineup, that might appeal to more reasonable people. If you like white beers (beer on lees is another term for this kind of beer) the Blanche is just awesome stuff.
All their beers are made in small batches using only natural ingredients. They're very popular in Quebec, and rightly so. There are even a few bars here in Krusty the K-town that bring in kegs from time to time....