Many open gun USPSA shooters still use 38 Super. I do see the newer shooters opting for 9mm Major in open guns although I fear that combination. I do use 38 Super with mild loads in 2 different revolvers a 6 shot S&W 686 and an 8 shot S&W 627.
I know .38 Supers can be shot out of a .357, but why would you do that?
.38 Super isn't dimensionally made for a .357 and .38 Special is a cheaper alternative...also, without clarifying your response someone might assume that one could shoot Supers out of a .38, which is a big NO-NO.