I did not attend the Bristol seminar unfortunately, but I've attended a previous seminar in Atlanta so maybe I can address some of the points. Joe, you are correct, there are many spiraling movements in aikido -- which is why I strongly feel that the techniques emphasized by Dan are 100% consistent with Aikido. I would say that Dan adds in a second spiral that goes in the opposite direction. This adds a qualitatively different feel to what the majority of us feel like when we spiral. I would LOVE LOVE LOVE it if this thread could somehow not turn into a "this isn't aikido" or "modern aikido sucks" argument (as I suspect others do as well). Dan has written quite a bit about his methodology on aikiweb, and after a single seminar, I am not an expert in Dan's particular flavor of aikido, so I'm not going to go into all the details. Rather, I will describe what I felt physically from Dan's aikido waza.
Here would be an example of how the in/yo felt to me as Dan was applying ikkyo to me off a shomen attack:
As I came in, there was very little external evidence of spiraling prior to contact with my attack. However, on contact I inexplicably started drifting off, kazushi taken. The odd part was the feeling of simultaneously having my attack get sucked in, while the space was being invaded. This was the in/yo dual-opposing spiral aspect of Dan's technique. I've commonly felt mainly in or mainly yo, but I haven't felt waza that was this balanced before (especially not with so little external movement). Thus, it does not feel overbearing (prickly spidey-sense going off as you attack), and it doesn't feel evasive (like the person isn't there anymore). I really just can't explain what it feels like! You just have to feel it for yourself. In any case, the dual-opposing spirals seem to happen in almost a fractal-like sense (i.e. at the point of contact, and on the whole of his body, and in you as you connect to "it").
Here is an example from a sankyo kaishiwaza:
Dan allowed me to get as full a sankyo as I possibly could and to let him know when I thought that it was sufficiently applied. I cranked it… said, "OK"… I hit the floor. Lots of things probably happened in-between, but the feeling was basically that I had applied a sankyo to a vitamix blender that was angled partially into the ground and someone punched it to 11. Again, it was not a prickly sensation of being attacked, it was just a balanced feeling where I just couldn't do anything about it. Now, some caveats -- He let me put him into an illusion of kazushi, but I'm not convinced that I actually had it as I was never really able to lock up his center. In fact, I'd say that I never really got to connect to his center, you just felt like you were connecting to the whole of him. This is different than the feeling you get when you apply technique to someone like Dan Messisco. Messisco feels like he is continually ahead of your technique, so the reversal is just him getting further ahead of you. He feels a bit more in than yo from my perspective. This isn't to say that Messisco cannot hit like a ton of bricks when he wants, but it feels different.
One thing that I appreciated about Dan Harden's demos was that he would turn the internal stuff on and off throughout. So, sometimes you would blow right through him, and other times you would get the "blender". This was important because as uke, you began to second guess whether or not you were really attacking or just drinking koolaid. Because it was internal, there were very few external cues to tell which you were going to get on contact. Anyways, those are my perspectives from an aikidoka who was skeptical and is now a card-carrying sycophant.