YAY!! Finally, something I can provide an informed answer to!! (hee hee)
I may be a rank beginner at Aikido, but I'm a highly experienced instructor and teacher in other fields. Being the Dojo 'Zip-kyu' (as I call it), I worried for a time that I'm holding the other students back in their development in Aikido - after all, I've only been doing it for a little over a month and a half; my ukemi is miserable, I have all the grace and 'big circular movement' of a Walmart mannequin. They have to spend more time teaching me the concept behind a move than practicing the move itself.
But then, let's stop for a moment and think about what we are learning Aikido for. Obviously, there are as many reasons for learning Aikido as there are learners, but there are a few regular responses. For instance: "I WANT TO GET BETTER AT AIKIDO"
No doubt. But think for a sec: Does working with a newbie take away your chance to improve? No, it does not, quite the opposite. When training among equally-skilled folk, you have less need to keep thing honest. The 1st kyu that's acting as your uke knows what's coming; she'll roll into it, or breakfall, or whatever without thinking. That's great, but if the idea is to develop Aikido as a self-defence technique, it's unrealistic.
Practicing with a newcomer, however, you have to deal with someone who DOESN'T know how to roll out; doesn't really know what's coming. As nage, you are now faced with having to do the technique perfectly, to avoid hurting uke. You also have to face all the problems that uke brings - foot position wrong, hand coming in from the wrong angle, etc. You may not learn more techniques, you learn more of each technique.
With a newbie like myself as nage, things get real interesting real quick; now you're faced with an entirely new challenge: teaching.
Experience at a skill doesn't give the ability to teach a skill; teaching is a skill in itself. There are NO natural teachers, EVERYONE has to learn first, and this is where you start learning.
I'm going to be hard-nosed about this; after fifteen years of active teaching experience, I can say without a shadow of a doubt; if your student (the newbie nage) is not learning a technique, its NOT due to his lack of experience at Aikido, its due to YOUR lack of experience as a teacher. I know; I've taught people ranging from physics professors to mentally challenged teens; my success rate makes this point for me. (No ego here. Yeah, right! LOL!!)
Remember, when you teach a technique, you have to place yourself in your student's position - what's obvious and crystal-clear to you may (and probably will) be a muddled, confusing mess to your student. You have to draw the fine line between taking things down to his level and condecension or going over his head; no question, it's hard, only experience can teach you that line.
"But Dave," you point out, "I want to learn Aikido, and I can't do that teaching this new dweeb!" Wrong again, sorry.
Teaching brings you to the very heart of a skill; you have to be able to analyse a technique and understand each and every one of its concepts in order to teach it to a newcomer; in other words; you have to KNOW that skill 100%. There's no question: it's frustrating. In almost every case I've ever seen, the new instructor was ready to throw up his hands and quit, blaming his student for his own lack. I was the same way, so was my instructor. So was yours, and his/hers. It's part of the learning process.
But doesn't taking all this time teaching a newcomer; and learning to teach, take away from your Aikido? No. You are an advanced student, yes? You are a Shodan, 1st Kyu, whatever; is the development of technique all you should be concerned about?
No! All Senseis were once newcomers; the advanced student of today is the Sensei of tomorrow. You may want to have your own Dojo. I do; and some day, I will. And if you do, you'd better know how to teach, hadn't you? I mean, REALLY know; not just try to imitate those teachers who have gone before.
Well, this (training with a newcomer) is where you start to learn; the grass-roots, if you will. In Aikido, in the Army (my area of expertise), at work, at play, this fact holds true. True, if you spend the time teaching a newcomer how Ikkyo works, you may lose the opportunity to learn Kokyunage-tori-link-lonki-ramma-lamma-ding-dong (I have NO idea what those advanced techniques are called. hee hee!), but you can learn that tomorrow, you have time. Your student needs you.