I did them for years in the belief that they would expand my ribcage. My feeling is that they probably don't do anything, but this isn't based on anything concrete.
Always found it an enjoyable exercise, however, and certainly seemed to help my flexibility.
Powerlifts: 500/363/573 @ 220 belt only
front squat: 403
dips: bodyweight + 176 x 4
military press: 232