I think I have like 7 different AFCK knives, all in different configurations (including the fully-serrated version).
I don't think you can lose no matter what model you pick, they are all fantastic knives. I have just a plain edge 800 ATS-34 uncoated that I use around the house for ripping open boxed and mail. I'll occasionally spray it down with WD40 to get all the tape gum off it and will touch it up on a Spyderco Sharpmaker, which makes it _really_ sharp (they should bundle the Sharpmaker with the AFCK!). Fantastic knive, really holds up well.
The only gripe I've heard is that the sort of "false edge" grind contribute to a weak tip. I've never broken a tip off but I've also kept this in mind when I'm doing any sort of digging with it. Outside of that you usually only hear great things about the AFCK.
The M2 steel (800HSS) ones are the real "choice" ones if you can find them. They did a limited run and they are pretty much all gone. You can get this thing so sharp that the hairs will leap from your arm just at the sight of the blade and it keeps an edge for a very long time and is easy to touch up.
--Doug