What i like most about the Hombu-style Aikido embu is the spontaneous flow. Doshu and a lot of shihan seem to always perform the exactly appropriate technique for the attack. This is something unique to Aikido that makes it stand out among other martial arts IMO.
(Note: if I ever find out these things are rehearsed, I am out of here.)
You honestly don't think they are rehearsed? Even if the flow of attacks isn't completely rehearsed, the way uke's are directed where to attack and the measured way in which they do so is practically the same thing. Though I'd still be they're hardly spontaneous.