What can I even say about these things?  They've been around forever.  They're totally comfortable (especially after wearing them for a couple days as they mold to your feet over time).  Wish I could still get them in the dark leather but Birkenstock no longer offers that in my size (48).  I wear them a ton and usually get 2-3 years out of them before they need to be replaced.  Found them here on Amazon for cheaper than anywhere else.