Shouldn't have worried about this before riding it.
My wife got used to things very quickly, and absolutely loves it.
PAS 0, using the throttle on uphills, is very easy.
PAS 1, with occasional pedaling, keeps a slower speed if she wants it, and is also very easy.
PAS 2-5, if she wants to cruise way ahead of me, while turning around and grinning frequently!
I've reminded both her and her friend to not ignore the mechanical gears, choosing the appropriate cog (or number!) depending on the terrain encountered and speed desired.
I put two of the Pace 500's together recently, and was overall very impressed.
I took some notes...and will post a new thread with some tips and observations soon.