I think you are right, Martyn...I am sure there is a bit of a differnce, but $429 worth...I doubt that very much. Was slated to shoot in the band room but they were having some ceiling issues and had to move out for the day, so instead went to the dance studio.
None of the girls were in "dress," only practice tights, but it was good practice to see how the lens would perform at different apertures, shutter combinations. So far, I am quite pleased with this lens and the opportunity it provides in shooting in tighter quarters with great sharpness.