Bladescout almost says it all. I have the same setup - Skrama, puukko 110 and 140 and the mini puukko bare tang. All are great blades for the price, and not only for the price but just that: good blades. Basically, if you have those, you don't really need anything else except 1) a thin-bladed pocket knife for fine slicing cuts (to stay within the price/quality range, I'd suggest an Opinel), a multitool for the pliers and other small tools; or if you are a knife nut like most of us, just because you may want something that looks nicer with noble wood handle scales, micarta, supersteel blade etc. etc. - but there you are talking about want, not real need. Of course most people who buy sturdy, practical blades like this probably already have one or more Moras, a Hultafors, something like that. This is really the next giant step up.
Some of my own personal observations:
- Skrama: you can improve it if you sand down the 'knob' on the handle a bit that separates the two grip positions, so it won't press so much into your ring finger when you choke up on the blade; you can also thin the edge as the 80CrV2 steel can really take a beating even with a keener edge bevel (best is convex for its chopping use) - I thinned/convexed mine and went from very good to absolutely awesome. A magnificent delimbing and splitting tool. As far as the sheath is concerned, the Skrama is a very large blade that I would not carry on my belt. If you just throw it in the boot of your car or in a pack, the standard blade protector will do fine as it retains the blade pretty well. I got the molle sheath with it and attached a sling so I can carry it baldric style, which works very well.
The puukko 110 and 140: both great. Get the sheaths with them, they are awesome (the retainment system with the snap button will likely withstand being launched into orbit strapped upside-down to a SpaceX rocket and when unsnapped, still retains the knife fine even upside down, while allowing for comfortable and silent unsheathing and sheathing - it's the sheath the Peltonen Sissipuukkos should have had, save for a loop on the back to enable strapping it to a tactical harness or backpack shoulder strap).
Note that these knives do not have scandi grinds but sabre grinds with a small secondary edge bevel. It allows for a keener main grind than would have been possible with a full scandi, and works pretty well. Convex them over time on a stropping belt and they will get even better. I don't much care for shaving with sturdy outdoor knives, I do care about holding a good working edge and they do that fine.
As far as the usefulness of the 110 vs the 140: I first had the 140 and found that it chopped way above its weight and size. I used it a lot for delimbing and light splitting. Then I got the Skrama and now the 140 sees far less use. Still, it's a great multifunctional knife to carry as your only fixed blade next to an EDC folder/multitool. If you have the Skrama, the 110 is the logical companion.
Finally, the mini puukko bare tang. Most people buy these to make their own handle. I did not. I got the flat leather sheath with it and now I have a very sturdy flat blade that I can use for food prep - very good at that as it has a keener, higher grind than it's big brothers, I use it daily to cut bread and cheese, and as there is no handle it is easy to clean - and on the other hand, a small blade that I can whack to split wood as I don't need to worry about damaging a handle, I can hit the tang. And it takes up little room in a jacket pocket or shoulder bag.
So: Skrama plus 110 for yard work or car camping, 140 plus mini bare tang for hiking where the Skrama is a bit too much to carry but you still want to take some indestructible edged steel for peace of mind.
The forge residue on the blades is not a deliberate coating, my guess is that it's a result of cooling the blades in oil. I found that it tends to stick to certain things you cut - cheese in particular. You can get rid of most of it with fine steel wool or even a kitchen sponge pad, and just leave a greyish layer. Looks rough enough, does not leave sooty residue in your food.
I'm only talking about the carbon steel versions here. The 80CrV2 is a ridiculously tough steel. The stainless versions use 12C27, which is OK but according to people who have compared them, not nearly as good as the carbon steel. You'd still get a very decent knife for the price, but not awesome (except for the sheaths of course). Go for awesome. ;-)