The Umnum took a while for me to love.
There was no doubt that when holding the knife, I was holding something well thought out, and carefully made; a serious piece of hardware.
However, the concept of the opening the knife via pushing the thumbstud straight up and not outward was confusing to my muscle memory, along with the fact that it was tip up carry, versus all of my previous models which were tip-down carry, compounded by the low profile, versus my previous which rode fairly high in a pocket.
But those are just details. Small, trivial factors really, much like carrying a different gun. The lock-up is extremely solid, and gives me no reserves in its ability to perform.
My only complaint, real complaint is that my thumb has taken a serious beating from the lockbar, disengaging it. A lot of people do not have this problem, just a few, me being one of them. I don't consider myself to have super rough hands, but I also don't think I have the softest either. I just wish the lockbar was dehorned a little bit more, and larger.
The newer models had a little bit of difference in the frame lock, allowing for easier access for gloves users.
I really do love my Umnum though. Simple, clean design with beautiful lines, and solid performance. Its certainly an eye pleaser when I take it out (among people who like knives. It still has yet to win over the wide-eyed crowd.)