Atemi is useful to know, but relying on it to make a technique work is poor technique.
Bingo. Besides, atemi is most effective after you have kuzushi.
It's even better when you have them on the ground and they can't move their arms.
If you think I'm not being "aiki" about this, please check out the Noma dojo photos and how OSensei is positioned at the end of almost every technique.
We don't shy away from atemi, but it gets frustrating to talk about because, like Ignatius mentions, most people think of atemi as simplistic strikes added on top of or around an aikido technique. Our movements simply *are* atemi. By that I mean that the movements we do are basically all strikes and most impact into uke's core to some extent. The way most people use it is a kind of pantomime of a strike, often at the beginning of a scenario, again to "soften" the attacker. My biggest issue with this is that it stacks the deck in favor of nage. After all, uke is often restricted to one big dumb lunge attack. So uke makes a big solid *single* attack, and nage gets to jump off the line, strike them three times and then lay on a big ol' kotegaeshi. The problem is that as soon as someone starts striking like that at me, I'm going to start deflecting and striking back. Now we're sparring. That's cool, we can do that, but you're not going to get kotegaeshi on me that way...
Here's a great video
to help show what I'm talking about. I'm sure William will enjoy it too.
So pay attention to what parts of Kondo Sensei's movements are strikes or cuts in the paired practice with swords. Basically everything he does is a strike, a cut or a positioning move in order to strike or cut. Although this is Daito Ryu, this is really the genius of Nishio Sensei's system as well. Now watch his movements in the open hand portion. Many things that don't look like atemi (particularly the initial entry) simply *have* to be done as atemi for aiki to happen. This is a lot harder to see in the video of me and Jeremy that I posted, but it's very much the case.