I was really surprised at how sweet this little movie is. I don't know why it didn't get better reviews. Rogen plays Andrew Brewster, an awkward chemist trying to hawk a cleaning product (Scioclean) he has developed. Streisand plays his widowed mother Joyce, who spends a tremendous amount of time meddling in her son's life. In an attempt to help Joyce break out of her rut, Andrew suggests they take a Mother-Son road trip across the country together. Unfortunately, that description sells this movie about as well as Rogen's character sells Scioclean.
Streisand is very watchable as the chatterbox Jewish mother. She's a fantastic actor, experienced and relaxed, who knows how to sell a scene without being schmaltzy. Rogen is not his usual "hammy" self in The Guilt Trip. He plays the uncomfortably stiff Andrew flawlessly. Mother and son each believe they have the answer to the other's "problems". Like most road trips, they discover more about themselves and each other than they expected.