All i can do is share my experience.
There are certainly some custom knives that rival or even beat the Sebenza in looks, materials, design, ergonomics, etc, and there are even some customs that might have slightly better fit and finish, BUT, i will say that the fit and finish on a Sebenza is not only just about perfect, and really tough to beat, even for a custom maker, but remarkable because this perfection and precision is so incredibly consistant knife to knife, whereas in my experience, you dont find that same consistancy when buying custom knives, even from many of the top makers. I find it all too common to see several customs by a well regarded maker, all beautifully made, and then see another of his knives with, for example, an off center blade, or a liner or framelock that engages the blade too far to the right. It seems that many custom makers, even some of the top guys, can't match the consistancy that CRK has.
And, ill say this, there may be custom knives that you like more than a Sebenza, for any number of reasons, but VERY few knives have better fit and finish than a Sebenza, and i will make the bold statement that NO custom knife "blows away" the quality, fit and finish of the Sebenza, because that just isnt possible, you may not like its looks, you might prefer a different design, or different, fancier materials, whatever, thats your taste, but to say any knife blows away the Sebenza in fit and finish is plain silly. They are so consistantly smooth and perfect, i have never seen one that wasnt about as perfect as a knife can be, and thats very tough to beat.
I have owned and examined a lot of customs, from tacticals to expensive, very upscale folders, and when i order a custom, i know its a crapshoot, and that theres a fair chance the knife will disappoint me with one or more flaws like slight blade play, poor lock engagement, or a poorly centered blade, in fact, i have seen all of these flaws in customs from some very highly regarded makers, but when i order a Sebenza, i have no fear, i fully expect it will arrive with none of these flaws and absolutely perfect, because i have yet to see one that wasnt, and unfortunately, the same cannot be said for many customs.
Again, im not saying the Sebenza is the best knife out there, or better than a custom, what I AM saying is that the Sebenza is remarkable for being so consistantly flawless knife to knife, and when you think of how many of them are made, the fact that they are so consistant is astounding and something every factory or even custom maker can aspire to.
Flame away, but it is absolutely my experience that you are more likely to encounter a flaw in a custom than a Sebenza. Your experience may be different, but, as i said at the beginning, this is MY experience. And, if youre a perfectionist like me and are very disappointed by flaws, a Sebenza may be your best bet, again, not neccessarily the best knife, but it will probably satisfy your craving for perfection better than many customs could.