Character growth may or may not be possible for Sheldon--who may or may not have learned certain lessons in the episode, as the show tends to reset back to equilibrium--but his mother, played by Laurie Metcalf, is guaranteed to by funny as she is in "The Rhinitis Revelation." With her around, Sheldon is still crazy but kept in check, making him more endearing than obnoxious. Mary herself is very pleasant, with her Texasisms coming off rather sweet.
There was a surprising amount of continuity in this week's episode. Howard going to the International Space Station is still on, Priya is mentioned several times in the episode, and Sheldon's weird relationship with Amy is at the forefront. Alas, when Mary talks with Raj, the writers already forgot about Raj's relationship a couple episodes ago.