BR: I suppose that you did learn that you won't pass out at the sight of a severe cut. That's something, at least. The shooting instructor for the Nashville PD once remarked to me that in a knife fight (when both you and the other combatant have knives), it's not a question of whether you're going to get cut. It's a question of how badly.
I totally disagree that sofas are "PERFECT practice targets for knife fighting situations". Sofas don't move. People do. Seems to me if you want the perfect practice target, you'd actually train with a live combatant and dummy blades. Or join the Marines.
I recognize that this "testing" MIGHT give you some information about how a knife will perform in combat. But I would remind anyone that knife combat is something to consider long and hard before you make it an automatic response.
Faced with a knife-wielding assailant, your best course of action is to run. Even if you're a trained commando, pulling your own knife and squaring off will likely get you hurt--possibly killed. And of course, if you stab and kill an unarmed man with a knife, regardless of his size, chances are a jury won't look too kindly upon you. Nor will the judge in the civil suit when he's awarding damages.
In a life-threatening situation where someone pulls a knife on me, I'll rely on my swift legs. If I can't get away, I'll go to the 9mm on my hip. Pulling a knife is just too often a lose-lose scenario in most combat situations. You'd only want to stab someone in the most dire of circumstances, and considering the death grip you'll have on your knife, I doubt it matters if its scales are G-10 or aluminum.
I know this post borders on a rant, but like mnblade, I sometimes grow tired of the self-professed Rambos on the board who are constantly testing their knives for "combat situations." I wonder how many of them have even been in a fist fight.