I recently tried No. 11 which was a straight-forward leather. Straight-forward in the sense that its sole raison d'etre is to be the best 'pure' leather in existence. in my opinion it suceeds. Its anything but simple though. I found it fabulously rich and deep. I bought something else in the end and slightly regretted it but I never enquired about the price. I since understand that they are tremendously expensive (at least for my budget).
I really can't stop thinking about No. 11. I found it that good. I hope one day by good fortune to be able to purchase a bottle.