The original point of the .357 Sig was to match the .357 magnum's ballistics. In the press of the day, the .357 Mag with 125 gr bullets at 1400+ fps was considered the "ultimate stopper" in handgun ammo. The .357 Sig was designed to match that performance, but still fit into a 9mm framed semi-auto.
In factory ammo, they seem to work well, and feed reliably.
Handloaded, I'd urge caution. Because the base of the bullet is hanging in space inside the case, setback in feeding may be more likely. I've never loaded for the .357 Sig, but I did work with its big brother, the .400 Cor-Bon, and you had to be damn careful with it to avoid the problem.
I guess the .357 Sig might be a more reliable feeder, than say the .40, but good .40's run reliably, and there's just not that much difference in real performance, according to the most recent data. If you're using a 1911, you can get the same performance out of the .38 Super, or the 9x23, and have another round in the mag.
If you've got a 10mm 1911, then a barrel change alone will let you shoot the .357 Sig, which is sorta neat.
