I agree that flow is incredibly important, and probably the one major thing that will make me take a second look. Blocky shapes, edgy corners on the handle and stuff like that will make me turn my nose up and walk away. The general design needs to be usable; I couldn't care less about "fantasy" knives.
Next I'll look at fit and finish. Yup, I'm one of those annoying guys that will turn a knife over, peek at the way light reflects off the surfaces, examine whether the plunges match and are centered, etc. I tend to think of sharpness as being part of this. Sound construction techniques are of course a big factor.
Feel is important too. If the knife feels clumsy or the balance is weird, I'll set it down pretty quick. The handle should almost feel like I'm not holding anything, just kind of rest in my hand, but stay there without me having to hold on for dear life. Does that make any sense?
The materials are almost secondary at that point. There are so many really good steels, and natural or synthetic handle materials available these days. We're pretty spoiled when you think about it. Nor do I care very much whether the blade was forged, ground, or made on a CNC machine.
One thing I really don't like is "too much" on a knife. This may be a touchy subject, but knives with damascus blades, mokume bolsters, heat-colored titanium, heavily figured woods, mosaic pins, gold inlays, gemstones, filework AND engraved everything are just too "busy looking" for my taste. Sometimes I think people are trying to cram every possible design feature into one knife and I don't care for that, it makes my eyes hurt. I enjoy a little more subtlety, like one or two of those fancy extra touches, but not every single one on the same piece.