Twice in a real SD situation I've used the throat strike with the axe/blade/sword hand and it's helped me to get away from the danger. On the first one it was a glancing blow but enough contact/force was made to cause the guy to back off holding their throat and fall to his knees gasping for air. They lived.
The second one was hard slash directly across the wind-pipe (aimed for the apple) with (my) intent to incapacitate quickly as possible, as he had a knife. He went down dropping his weapon and likewise holding his throat. I walked off... didn't look back... and at the time didn't care.
So yeah, I'd say they're effective if you execute it correctly and get in a good strike.
I have used the strike and piercing or stabbing many times in self defense on the street type encounters and also with those guys who always try something at a seminar or a new class.
I think the strikes are possibley deadly.
I also think they are also good for over all training and control.
I was invited to a JuJitsu class back in the early/mid 90's and the guy who invited me did not show up. So I was going to leave. The instructor asked me to stay. I did. I was paired up with a black belt from the club. The head instructor not sure of what rank of black he was, but has recently been to a BJJ seminar and was going to talk and demonstrate some stuff.
I got paired up up like I said. This guy decided to not work on what the top instructor was working on. He was going to tap me out, which I learned in this process was also supposed to make me pass out. He went in for a neck choke from a top mount. I know there are chokes there. The problem is that I could breath, but I could feel the vertebra slipping and compressing. I asked him to stop. He did not. I tapped and told him to stop. He did not. I then poked him in the throat which caused his arms to straighten out where I did a small circle lock on his write and threw him while also moving my hips to roll him over. I was then in his guard, but able to get him into the same choke. I told him what the choke was as he could not breath and then showed him the neck compression he was doing on me. He tapped so much and his friends who had been laughing at me were not yelling at me to stop as he was tapping out. I got him to the point of just passing out then let go, and stood up and asked to leave. The instructor asked me to stay not knowing the full story but he then paired me with this 350+ pound guy who was over 6'5". I could not even get my arms around him. I had to have staind to straddle him in the mount. I explained to the instructor the issue at the end of class. He udnerstood and said he would talk the Black belt and asked me why I was wearing a white belt. I told him that my dirty white belt is what I wear when invited to other clubs to train, not as a guest. He smiled, and asked me to stay with him. I told him I was not up for it giving the experience I had.
The point is that with a proper throat jab/stab I was able to stop this guy from hurting me and possible permanently hurting me for his pelasure and or ego or some initiation to his little group. He was not harmed permanently and he was able to continue to train after he came around after the choke. So, I like them and with proper usage they have their places.