I will not rank who I prefer to deal with, but the group, in no order...
Neil at True North
Larry Amoruso at Three Little Indians Custom Knives
Arizona Custom Knives
Steel Addiction
Bladeart
Many other smaller collectors with collections up - knifeology for one
Knifeart has nice knives. I do fully respect, understand, and appreciate their policy of selling only new knives. They ship fast too. And I do buy from them.
As a customer with regard to a long term relationship, for me what is important, however, is not how "good" a vendor or sites does things, but how they react when things take a sh!t or just don't turn out.
I am honest with you, respect you, and trust you with thousands of dollars. Show the same reciprocity and treat me the same if things don't go as planned. It's not asking for a lot and is solid bedrock for long term business.
I will not comment specifically on knifeart except to say what I have said - good knives, upfront pricing, fast shipping, but several instances from reliable sources have given me pause.
And...all the guys in my list above will make it good if you are honest with them. You throw a line of bullshit, you get it in return. I have had knives returned to me because somebody "changed their mind", but in reality they dropped or scuffed it. Lesson to me. Again, the relationship is what matters. Some people get it, some don't, and some really don't give a shit either way.