I bought one of them The Naturals, large version. I'm kind of an enormous dude, I'm 6'7", so I really liked the size of it. My girlfriend sort of freaked out about how huge it was and in defending myself I found myself explaining "It's the size a knife has to be for it to feel to me like it feels to you all the time." It's a good thing she freaked out or I probably would not have made such an astute observation. It is very heavy but I find that cool. When you're holding it it let's you know about it. I found it comfortable in my pocket despite the weight.
One problem I had is it was *extremely* difficult to open. Like, to the point where I got sores on my thumbs from messing with it the same night I got it, just from opening it via the thumb stud. I couldn't even open the thing without planting a finger on the other side. I tried oiling it but it made very little difference. I agree with Allan45 that the pivot stud's location is off. In fact, I put another pivot stud in a hole closer to the bottom, from a different knife, and that helped a little but not enough. I poked around online and other people said it was hard to open but broke in with time. I'm pretty sure mine was unusual though cuz I was watching videos of all kinds of people effortlessly flicking the thing open with a thumb tip and mine wasn't even efficient to bother opening one-handed.
I wrote to the customer service, warranty in mind, and they were friendly and helpful. I ended up sending it back to them, they said they would fix it (for free). I mailed it 2 days ago, so we'll see how it goes, but I'm betting it will work out. I guess the main point is that the things are hard to open and some are really really hard to open ... or at least this one was.