I have a single Douk Douk, and I love it. Its simple the best looking pocket knife I own, its good looking in its ugliness.
Blade play is zero. Its a great blade steel, takes a super edge and seems to keep it well. It is also likely thicker than you think it is just from pictures, so I would guess its pretty stout.
Now to be honest, as an all around pocket knife that sees use, I have to place it below the Opinel. But it really is about you and where you live and how your knives get used...
The down side to the double D is its very strong back spring, and slick thin nature. It would not be the knife I'd want to pull out of my pocket here and now with outside temps being below freezing, plenty of snow on the ground, and a day of freezing rain. Its hard enough to open the blade in the kitchen with wet hands...add numb fingers to it and I think you have a good chance of going to get a bunch of stitches, if you can even get the blade open.
I put the Douk Douk away when it gets cold. I just think it is far safer this way. Now if you are in the warm sunny south, it may be fine 12 months a year...?
Its a beautiful knife to my eye, rides in the pocket like a steel stick of gum, and when open gives you one sharp blade, and does it with class.
if you call yourself a knife guy you should pick one up just to own, it may or may not fit in with your life style/location...but its very cool.