Andy (and our forum members),
Let's work backwards from the tasks the knife will need to perform in order for us to meet our needs in the woods. Andy, you can see from the general descriptions that the knife need not be a big chopper, but also not a tiny 2" blade. It should be able to work with wood extensively, and at a minute and detailed level: carving and whittling. The spine should be strong enough to take the beating of a baton, and the edge should be thin for expert slicing (I want to be able to shave wood into hair thin pieces, or carve chunks -- so it should be balanced in a way that I can use a high level of finesse, but also really drive it through different materials.) It should be able to skin an animal - AND clean the animal. You can skin an elephant with a 1-2" blade, but you need extra blade length to get up into the innards to remove them easily. A nice curved belly with a drop point or spear point, about 4-4.5" as many have said, does both well.
When you get into a 5" blade and above, you start to lose the ability for fine work (just barely), and when it goes to 6", 7" etc., it definitely starts -- depending on the blade geometry -- to move into the "one-job only" category: chopping. I want to be able to drill holes to start a fireboard, so the drop or spear point really makes this easier.
As others have mentioned, the most-used part of a bushcraft knife is the portion nearest the choil/handle. That's where you whittle, notch, and carve wood. The bellied tip is where you skin and dress game, and drill holes. If the choil is long and wide, or if it has a finger-choil cutout between handle and blade, it reduces or eliminates the ability to do this close work.
The handle should be smooth, minimal guard, and should not create hot spots from extensive use. It should be contoured just enough to keep your hand from slipping up onto the sharp edge easily, but still accomodate the ability to "choke up" and use the blade upside down to spin wood and notch it. The plane of the edge should not be too far below the plane of the bottom of the handle. When that happens, it's awkward to choke up on, whether upside down or right side up for whittling.
Full tang is a must, whether hidden, or exposed with scales. I prefer exposed tang with scales.
The balance should be just forward of the handle enough that it is not top heavy nor handle heavy. It should be fast in the hand and easy to control.
There's so much more, but hope my little addition to the other members' responses helps guide you.
Blade geometry should be convex. flat ground, or -- as some prefer -- Scandi (although I personally don't prefer that one to the others). Convex is king for me. I find that, with convex grinds, a smaller knife suddenly can do very big things - without losing the ability to still do the small.
No sabre or hollow grinds, no black coatings. They all impede on your ability to maximize control, or are too thick or too thin/weak to be all-around bushcraft blades.
First and foremost, we want the damn thing to cut and cut! Too many makers grind thick blades that are awesome for prying, but too thick and unwieldy to cut with. If it's tactical, it's not practical for WIlderness/Bushcraft.
