While I love my small Sebenza, I'm not particuarly fond of the thumb stud.
I find that it is a bit small (the tip actually - where my thumb contacts it) and a bit sharp.
The result is that it is slightly uncomfortable to operate at times. I carry the knife cliped into my front pants pocket and I've also had the grooves catch a loose string and pull the knife open slightly on a few occations resulting in a supprise when I put my hand in my pocket!
I would like to see a thumb stud that is similar to the diameter of the Sebenza stud (maybe a tad larger), about the same height, but is a simple cylinder with cross hatching on the top.
While I'm on the topic of things I don't like I should mention the open back design* requires a lot more care in carrying the knife as coins tend to find their way in and nick the edge, even while carried "clipped" in. I've had to re-train myself about coins after a few close calls.
That's it. That's all I don't like about it - two things.
Just in case you are worried - I love this knife. It is among a small collection of items that are with me always, regardless of where I am going or what I am doing.
-john
* I understand changing this would make the design more complicated and less elegant.