I have to agree with Aiki1, in that this subject is always in debate. At Shindai Aikikai we train in atemi probably more than a lot of dojos. Hooker sensei will sometimes devote entire classes to nothing but atemi. It does make contact, and your intention certianly is to strike the vital points, and very hard as well.
I believe the misconception regarding atemi happens while watching advanced people train. The more advanced you become, the more aware you become of the dynamics. When you see someone put a hand it the face of uke, the atemi is assumed and you will see the advanced uke react as if contact was made. This is done so that uke doesn't go home each night in pain and can continue training. Otherwise uke would not be able to attack more than a couple times.
Now, to the not so advanced, this looks rather funny to watch and the wrong idea regarding atemi is formed.
Once you've learned the "where" "how" and "why" of striking, then power and speed should be practiced on bags and not on uke.
Unfortunatly this can leave the wrong impression with new students or those just sitting on the side lines......
Dan P. - Mongo