Made these following the recipe in the Tartine baking book. The recipe is 7 pages long, took me 3 days, yacks, but the results are well worth the effort. You can find the recipe online here: http://kitchenmusings.com/2007/01/my_attempt_to_m.html  . I was a big fan of the bakery when I lived in CA, that's why I must try the recipe despite the intimidating details. We loved the crispy shell, crumbly texture biting in, and hollow, many layered, lighter than air crumb.
As far as taste goes, we loved how buttery they are. Long fermentation did add layers to the flavor, if we hadn't had the sourdough Pandoro a few months ago, we would've been 100% satisfied. However, being spoiled by that 90 hour Pandoro, we now think it could be improved if there's a bit more "tang". I am now searching for a good sourdough croissant recipe to try next.
Also made the chocolate variation, very good.
These are American sized huge croissants, just like how they sell them in the store. I made the whole recipe, but only used half of the dough for this batch, good call since otherwise we won't be able to finish them and my oven wouldn't have been big enough. For the other half, I will make smaller, more European style ones, so the ratio of the crispy shell would be higher.