Shooting .38sp out of my GP100 6" is in one word...FUN!!!!
Hardly any recoil (more of a push straight back), and more accurate than I can shoot.
Being able to shoot .38sp. is one of the reasons I bought a .357mag.
Shooting a double action revolver is a great way to learn trigger control.
I always start my range sessions with my GP100 with .38sp, then move to the 9's.