I got the 357sig itch a while back, when i owned a 40s&w glock 23. Bought an aftermarket barrel in 357sig.
I put some hot Doubletap 357sig ammo through it. Found I wasn't too impressed, in fact, I preferred the 40s&w.
The 357sig just didn't seem to be enough of an advance over the +P+ 9mm for me.