I owned a couple of them.
John Benner (TDI) has put much thought into making these blades work as they are intended. With the forward cant of the blade, the natural position in the hand makes it somewhat akin to a push dagger for forward thrusts, and small kukri for sweeping motions.
The finger reliefs are cut to allow a natural grip on the blade, without straining the hand, so, it feels quite natural. The jimping is there to re-enforce more traction for those sweeping motions.
From novice to expert, those that I have talked to and put the knife in their hand, says it feels like it would work very well should one be faced with using it as its intended purpose.
Also, for the Large TDI, you can also get a Trainer, which is very good to have as a companion to the real deal.
I do prefer the original, myself. Mostly, its demure size is much easier to conceal and when you whip it out cut a box open at the post office, folks don't look at you funny.
I practiced some center line, downward slashing motions on free hanging cardboard, to simulate a center line attack on a person.
It works, dramatically so.
Moose