Since the subject of the retracting hand was brought up, I thought I'd put in my two cents on that.
I practice at an ITF school, so my training is traditional. Master C.S. Kim goes to train at his old school, back in Korea, every so often, just to make sure that what he teaches his instructors (and what they teach us) stays correct.
One of those things, which has been pounded into me since I was about a red belt, was the concept of both hands moving together.
When we do pal po ki (in-place punches, if my spelling's off), even, the hand that punches can only go as fast as the one that comes back. This becomes especially important in blocks. In one-step sparring drills, there are a few where the defender's first move is a block in a fighting stance (back stance?). But without the other hand pulling back fast, it's harder to get any waist power into the block. That's why you have to use the trunk of the body to make the block effective.
It's like in that Karate Kid movie, where they had the hand drums with strings and balls on each side. As one hand goes out, the other has to come back. That, combined with landing hand and foot together, is how to get power behind techniques.
In response to Master Jay's comment about the opening of pyong ahn sam dan (the first move is turning your head to look!), I too just recently learned what exactly that move is - blocking two consecutive double-punches (a la Bassai Deh). I agree that a practical application wouldn't be expected to have you with feet together, but I'm sure there's another reason behind it...I'll have to ask my sa bom nim.
Back on the subject of how the forms changed, that's an interesting subject, though I don't think it changes how I practice at all. But I was first introduced to this idea by the video game Tekken 4, wherein the main character, Jin Kazama, is shown performing what to me was a lousy version of pyong ahn sa dan (
http://www.youtube.com/watch?v=n_z9rnHcjHM). If that's really how they teach it in the style he's supposed to have studied (some form of karate?), it's a bit laughable.
Anyway, I know I'm not an instructor, but all I'm saying here is what my sa bom nim has pounded into me. Hope it's helpful.
