Re: Speed in waza?
The basic question that rises is: who is slow and who is fast?
When training very slowly, often, inexperianced Uke re-stabilize themselvs from Kuzushi without noticing, or conversly, change the angular direction without the effects created by the momentum.
If you have such an Uke, you may find a fast technieue works much better then a slow one, regardless of your own mistakes.
This issue is part of the role of Uke in Aikido, he should give an honest attack, and respond realisticly, even if everything is scaled down (note, responding realisticly does not equate fall / impose technique on self, rather flowing with Tori actions as if the speed was much higher).