Actually, I've had some of those chocolate and coffee stouts.  I find many of them quite tasty, however all of them are one-and-done for me.  I'm not going to drink 3 or 4 of them while relaxing on my beach chair or watching a game.  I consider them to be a treat, not an 'everyday' beer.  When it comes to treat, I like a Sweet Baby Jesus once in awhile.