... partly because a knife sharpener guy totally destroyed my F1 and the U2.
...I also have a diamond sharpener glued to the S1 sheath. I dont really know when I should use it but it is there just in case...
I am sorry to hear about your F1 and U2 being destroyed by a knife sharpener guy

I once sent a knife for polishing and somehow the guy that did the job went wild with the polishing wheel and made a huge groove on the brass guard, got rid of grind lines and thinned out the tip so much that I am afraid now to take it out of the sheat. Never ever again. I was too young at the time to do anything about it but today I would ask for a replacement, that's for sure!
I also thought about getting a DC3 or DC4 sharpenning stone (the two sided one) so I can sharpen my knives in the field but... then I realised that I am convexing all my blades

. So unless I am truly desperate I wouldn't want to throw a bevel on my edges. I usually take short trips so the need for sharpenning in the field will rarely happen. I am thinking about making a portable convex sharpenning system (little piece of wood with properly sized sandpaper bits and maybe a little piece of loaded leather strop).
Plinthman, I own an F1 and a friend of mine owns an S1. I haven't had the chance to use it but owners state that the false edge on the S1, while helping in penetration, is hell on battons while splitting wood (not that you need to do it very often, just to let you know). The S1 is also thicker and has a saber-convex grind while the F1 is thinner and has a full convex grind. The F1 is better suited for food prep (think slicing). The handle on the S1 is bigger so if you have big paws or are going to use the knife with thick gloves on, you will be better suited with the S1. Other than that, I would get the F1 for general use. Whatever you get, get it with the nylon sheat. It is the cheapest and you don't need to baby it at all. You can just arrive home, take the knife out, dry it and rinse the sheat under the tap to get rid of dirt, grease, whatever...
Bark River Knife and Tool has a ton of knives with a lot of different handles to chose among but they are somewhat more expensive... and the leather sheaths, while pretty and usefull, are less tough than the Fallkniven nylon ones. Exposed tang knives like Fox River, Nebula, Aurora, Northstar, etc... may feel cold in the hand when used below zero glovless... you won't have a problem with Fallknivens because they all are hidden tangs (exposed a bit on the butt for hammering).
Mikel