Opinions?! Oh boy! I have some!
I like Tri-Ad locks, lockbacks, and AXIS/Crossbar locks.
Not a fan of frame- and liner-locks, after I had one try to unlock on me. It was completely my fault for trying to use the wrong tool for the job rather than taking the time to find the right tool. Still though, this takes my "git 'er done" attitude out of the mix.
I don't like thumb ramps anymore, or the jimping that usually goes with them. For my practical cutting requirements (as opposed to the occasional Mall ninja indulgence I allow myself), they just get in the way.
I like a more "neutral' handle shape, instead of something with curvaceous curves that are made to do some high-speed secure gripping thing.
I like modified wharncliffe blades, or something with a less pronounced belly. Think of Fiddleback Forge's work, and you'll see what I mean. For most of my cutting work, something with a steep belly (like a Ka-bar) just slips out of the intended cut.
G-10 and Micarta. Wood slabs for some knives.
Not a fan of bone, celluloid, the more traditional plastic choices, or this new Ultem trend. Big 'ol meh.
I have a 4-Max Scout, so I'm not totally against big folding knives for fun, but for most practical everydays, something around a 3" blade is the right size for me.
Pocket clips. Easy to pull, easy to clip, and needs to stay in my pocket, even if I fall out of an airplane. A difficult balance, as you might imagine. Cold Steel of all places, does it well.
Pocket clip screws. Yes, I have opinions about pocket clip screws. See, I've had clips come loose, just from walking around. A triangle-shaped screw pattern, like the Cold Steel Recon series, causes problems. I think the third screw acts as a fulcrum point against the other two, allowing them to eventually escape. So, I should really say that Cold Steel does it well, sometimes. Or maybe I just haven't carried my 4-Max enough to have this happen.
Not big on full flat grinds, or really thin blade tips. I'm a bit of a gorilla, and I don't trust myself with blade grinds toward the "high performance" end of matter seperation geometry.
Serrations. No thanks. I've tried and tried to like them, but I'm a town boy, and I don't cut much rope, or jungle vines, depending on how hardcore you want to be with your survival scenario. I would rather have a sharp blade to a serrated one.
I'm not interested in chasing the latest super steel.
I want companies to put Rc numbers in the information they send to retailers. At least, "target hardness" numbers.