Soncino has been used for a half century, only being phased out in some shuls when Artscroll became available. In many ways it isn’t as good as Artscroll, especially in bringing meforshim beyond the Rishonim like Ramban and Ibn Ezra that it quotes liberally in its commentary. Artscroll comprehensively brought the works of the Maharal’s extensive commentary, the Chasam Sofer, as well as Rishonim like (occasionally, when applicable) the Meiri, which Hertz didn’t have access to becasue his ksav yad wasnt rediscovered until after the Soncino editions went to print.
It is distinguished by not being hagiographical like Artscroll sometimes is, and it was also as described above a direct response to christological interpretations of our Tanach.
BTW, I can recall seeing it in use in Agudas Yisroel shuls a long time ago, so it wasn’t only the MO who used it.
I’m personally very impressed with the Koren series of publications, which take the strengths of both the Soncino and Artscroll approaches and overcomes their weaknesses.