I have gone through many knives, most recently the Seal PUP, which is a great one. I always find myself going back to the USAF survival knife-its robust, simple, and, to be honest, I like the weathered look of the leather handle after a few years of use .
The one thing I have noticed with it, and this is from recent observation, is that if I use it to baton, the baton itself ends up getting pretty chewed up due to the agressive ridges on the spine. But, honestly, thats a relatively minor inconvenience for me. I dont use the leather sheath it originally came with; I actually use the kydex one that the seal pup was shipped in. I like it for its versatility, and simplicity. I dont see a need of field sharpening, and, if that was required, I usually carry a diamond honing stone in a pack.
The upside is that, you can find these knives literally anywhere, and they are usually pretty cheap.