I agree with all that's been said, good point on the R&D--they are very committed to testing and improving their products.
I think the key element are that they simply do not cut corners--whether it's in the design (ergonomics, cutting performance) or the materials. They don't stop at acceptable, they strive for excellence. For example their steel selection--I look at a lot of other companies, and see knives for $50 in AUS-8 or even 420HC..not to disparage those steels, they are great for what they are, but certainly not high performance by today's standards. I just shake my head and thank God for Spyderco.
I seriously cannot believe I'm getting a Para 2 in quite possibly the highest-performing knife steel in existence, and it's costing my well under $150 (I'm a lucky one whose pre-order came through, so I don't have to pay ridiculous gouged prices).
I think one thing that causes Spyderco to be such a great company is the fact that they truly have a
passion for what they do. They are knife users and lovers, and seem to be just as if not more enthusiastic than the us enthusiasts on the forums.
Also, I think they are simply good, honest, ethical people. They are not just in this to make money. They know there is much more to life than that. I think that they do this because it's what they love, and they provide an amazing service to the knife community by providing cutting-edge (no pun intended) cutlery at a very fair price. A great testament to their ethical nature is all of the models that support great causes. Different knives they make or have made support Alzheimer's, AIDS in Africa, Breast Cancer, September 11 terrorist attacks, and the brave troops fighting in Iraq and Afghanistan.
Their pursuit of excellence in the industry and in life inspires me, and makes me proud to carry a Spyderco every day! I know, I'm gushing