Hi. I am new to the forum and fairly new to Aikido. I have been training for less than 2 years now. I hold the rank of Ikyu and hope to attain Shodon in a couple of months. I say that not to brag but to say that I am close to having a good grasp of the basics of Aiki (at least, I hope so
As I understand atemi (which is just a pretty basic understanding at this point) it seems that everything we do should carry at least a small amount of it. I view atemi as "intentionality" or, if you like, the projection of your ki in such a way as to alter your opponent in some fashion. This can be done through atemi-waza or kansetsu-waza with the common notion being that both must start from the ground. Any force that we apply that doesn't come from the ground, through our opponent, will be ineffectual.
It is this ineffectuality that, at least in my dojo, leads to kata being more dance-like and less martial. Uke just does what they're supposed to for tori to complete the technique. This is how kuzushi get's sloppy and technique in general begins to degrade.
Recently, while preparing for a demo, we decided to use more "realistic" strikes. We did this simply because "outsiders" don't generally understand the types of attacks we use. The unintended result of this is that uke was attacking with force and intentionality and tori was forced to respond in kind. Although a little intimidating for lower ranks, it made for a great demo and illustrated nicely the need for atemi by both uke and tori. We are currently thinking of how to incorporate this type of practice into our normal randori regimine.