Opinel by
Pinnah, on Flickr
Great knives but not for everyone.
Couple of comments...
First, there is no single Opinel. The different sizes are very different knives so you need to match the size to the need. The #8 (bottom of the pictured ones above) is the most popular. It gives a tight 4 finger grip for M to L hands (as in glove size). Feels like a folding paring knife to me. The blade is thin and flexible but the knife is tougher than it looks. The 6 and 7 are more like small pocket knives. The 9 (the middle knife) gives my XL hand a solid 4 finger grip and still easily carried in the pocket. It's by far favorite EDC and hard use knife. The #10 (top) is as big or bigger than a Buck 110 and IME tougher to boot. It's a bit too big for pocket carry but I keep one in my backcountry kit as a light back up knife.
Second, they are crude when new and need some tuning up to take them from crude to nice. If a person is looking for something that is totally maintenance free, they should look elsewhere.
Third, obviously, is the styling, which is not to everyone's tastes. YMMV territory. Personally, I find they are more socially acceptable and deploy my #9 in places where even a smaller modern flipper would scare people.
In terms of cutting performance, I think they're amazing. The steel is good and joint is very, very tough. The lock doesn't foul with dirt and sand and is very reliable (so long as you pay attention to it and don't stand on the handle). It's the sort of knife you can drop in the dirt and not worry that the lock up will be less secure. It will make noise, but it still works and I can't say that for any liner lock or lock back I've owned. The blades are thin and slightly convexed. They go through wood, vegetables and cardboard well. For hunting, fishing or meat processing, a hollow grind might be preferred.
The carbon steel is close to 1085 and hardened around 56Rc according to reports. It is very tough, dents before it chips but doesn't have the edge retention of 1095 hardened in the 58Rc range (e.g. old Schrade USA among others). The Inox is Sandvik 12C27 hardened to the 58-59Rc range according to reports. It takes an incredibly fine edge, is reasonably tough and holds an edge like good, hard 1095. My recommendation is to use the Carbon if you cut stuff that bumps into metal. Otherwise, go with the Inox.