Liked the concept. You can delete the memories but not the chemistry between two lovers. Loved the way how it was shown through a subplot between the doctor and his assistant. The sparks will continue to fly. That's why, Clem feeling attracted towards Joel in the train finds justification in retrospect.
One star less for the dragged middle portion of the narrative. Lot of instances of erasing Joel's memories appeared repetitive and superfluous after a while.
Nice watching, for once though.