I was giving this thread a pass, but I'm in the mood to run my mouth today* so I thought I'd weigh in with a defense of the "Aikido as moving meditation" point of view.
The main form of mediation I'm at all familiar with is zazen. That practice, as I understand it, is a practice of mindfulness--how to be fully present in the moment without distraction and without the constant second-guessing so many of us are prone to--the little voice constantly looking over your shoulder, evaluating your performance, and commenting on your actions. The first thing you learn practicing zazen, of course, is how hard it is to keep the mind focused--it's constantly haring off after one shiny object or another.
But zazen is just kindergarten practice. By removing most external stimuli, it makes the task of staying focused as simple as possible (and even there, most of us mostly fail). The ultimate goal is to be able to take this focused, centered mind back into the marketplace (a Zen phrase). Many of the stories and koans Zen practitioners tell show how a Zen master brought his clarity of mind to real-life situations. (Which is not all sweetness and light. One monk regularly told a story about how her teacher's clarity of mind led him to throw her elaborate flower arrangement out out in the front yard as soon as he saw it.)
The point is, in these stories, that the protagonist isn't acting out of their own preconceptions, prejudices, or assumptions, but simply as a reflection of what's there. The enlightened mind, as they say, is like a still pool--when there's a cloud it reflects the cloud. When there's no cloud, it reflects blue sky.
The monastery where I studied would regularly include activities designed to encourage you to attempt to take this clarity of focus out into other activities (cleaning bathrooms, chopping vegetables, etc.).
So with Aikido. On a good day, an Aikido technique can be a context in which to practice the same kind of focus. When I'm responding to the attack uke has given me, I can respond out of my idea of what they ought to be doing. I can respond out of my idea of the technique I think I ought to be practicing. Or I can just respond to the needs of the moment--without planning, without thought. Obviously, this is a trained response, but not all that trained--I first started to (occasionally) have this experience only a few years in.
And it's practiced just as well as uke. To simultaneously deliver a real attack, protect against openings, and respond to whatever technique is applied to you requires that you give up any idea that you are controlling what happens--you are simply present in the moment. Sometimes what happens in the moment is kaeshi waza, and that's fine too--but it's not the point. The point is that good defense comes out of mushin and being alive to the possibilities of the moment.
* Dark & Stormy, sunshine, Embarcadero