But I'll try, because the movie is just extraordinary.
Stage Beauty is conceived much like a play by Shakespeare, with its layers of complexity behind the apparent simplicity of its powerful story, its well-crafted characters, and its underlying themes (interactions between genders, definition and pursuit of Excellence, disorder versus order). In fact, it is highly reminiscent of Othello in its central themes - and, not surprisingly, Othello the play is at the heart of the movie.
The performance of the actors is simply stunning - they effortlessly take viewers from one emotion to the next; and watching them portray players who in turn play roles (of their own gender or not) is an absolute delight.
However, acting skills are enablers - what really allows the cast to deliver such a compelling performance is the movie's overall structure, and the consistent way in which it deals with its core themes. In fact, the movie progresses in such an irresistible way that it culminates with a man and a woman simply greeting each other before a rehearsal - the masculine Excellence and the feminine Excellence, finally defined, and facing each other at last - after a period of disorder and conflicts.
An absolute jewel.