The caricatures of the out of work actors (Jolson, Benny, Cantor, Crosby) are what almost all of their caricatures end up being: simultaneously self-serving, and obsequious product placements. Mind you, there’s at least a little poignant, film-historical truth to the Jolson and Cantor situatios.
As for the film itself, it benefits from some effective, dead-pan repetitions. “Oh! We’re the boys of the chorus…” Unlike the cameos, the dig at hunting pictures is quite funny. I very much like that we hear the whole song.