I think that the atemi in Aikido is not really meant for striking per say. It is used more in conjunction with entering, or irimi, in order to take and control uke's space. Of course you can make it into a powerful strike if you choose to actually have it connect with uke, but we (usually
) don't do this.
We do in my dojo.
To my mind, atemi is the mirror of ukemi. One is about receiving force with the entire body, the other is about delivering force with the entire body. Used together, one can receive and deliver force which is the beginnings of aiki.