Before studying aikido, I studied Ryukyu Kempo for 8 years. It was a hard, vicious style. This form of Kempo has three main components. Twite-jitsu (joint locks), Bunkai (breakdown of kata), and Kyusho-jitsu (nerve strikes). I believe it has aided my atemi-waza. The only problem is that even though I earned my Nidan, I could still only get the reaction I wanted about 50% of the time. It is not easy.
In many cases in aikido we use nerve manipulation as part of the art. Yonkyo is technically kyusho-jitsu. When we practice iriminage, we often use carotid pressure to "pin" uke's head to our chest while performing tenkan.
I think the longer you practice aikido the more the use of these techniques becomes evident. The thing is, the use of kyusho-jitsu in aikido should be an after thought to learning the technique and applying ki correctly.
It should not be used as a short-cut to force techniques to work. This would be contradictory to the entire idea of blending completely, and losing one's self and ego, that is so important to aikido.