The upside is........
Obviously with a condition like this you would keep daily records - and every day would be fresh as far as love and sex goes so that's a plus, it would never get boring or stale for him which would also keep it fresh for her.
Obviously the down side are much more so I won't go into that.
Personally I dislike my past and would love to wake up every morning with a new love of my life per se albeit it being the same person.