That is really not that much different than Kata-garuma in Judo. Only in the judo version uke isn't making the throw that easy for tori / nage. Having done the Aikido and Judo versions I can say that the fall is also much harder in the judo version as uke does not have as much control during the fall.
The fall / ukemi itself is not very hard to do. It is all a mental exercize. The first time i was thrown this way in Aikido I had no idea it was coming and I took the fall just like any other fall. Knowing that I had already done it, and it wasn't bad, I never had any issue taking that ukemi again. Had I known what was coming the first time I am not so sure I could have taken the ukemi as well.