I have a two gun case that I originally bought for a pair of consecutively serial numbered Browning O/U's. I'll admit that I really wanted the case to keep the guns together for display purposes most of all but did use the case for hunting a couple of times. My opinion now is that I won't take it for anything rougher than a preserve shoot where I can lower the gate on my truck and open it up while getting ready in a somewhat controlled environment. They are too big and bulky to keep on the back seat and maneuver to get ready with ease especially on the side of the road which brings me to my second reason. I don't want the world to see the case while I'm getting ready at a trailhead or the side of the road. Not everybody is honest and if someone with bad intentions sees you open your $1,000 tan leather case, take out one of two $5,000 shotguns and then walk away into the woods you might not be happy when you get back to your truck.
I typically assemble my guns at home and slip them in very thickly padded cases that I got from CSMC. I still bring two guns every time because I have had a malfunction that ruined a trip long ago so lesson learned. I hide my extra gun as best I can inside the locked truck, making sure to always cover it with extra clothing or whatever is handy.
Bottom line is that double cases are not that practical for a lot of hunting situations but they are really nice for displaying your guns in a more social or controlled environment.
Like I said, I have a double case and I like it. I plan on keeping it forever, but I would never buy another one even though I have several sets of "paired" guns.