What were the Gedolim's (Torah greats') reaction to ArtScroll and later the Schottenstein Talmud? I'm wondering what accounts exist of the various Gedolim's reactions to the company/proposal.
Most Gedolim who they asked agreed. (The initial idea that they write a gemora was the suggestion of Rav Yaakov Kamenetsky)
Some of the Gedolim who primarily dealt with the more learned crowd were opposed due to the fear that "when there is an easier option the harder one becomes impossible" and the Artscroll Gemara would cause many people to lose their ability to understand Gemara without it. None of them said so in very public forums.
Rav Shach was opposed to it for the reason given above. He considered saying so publicly but decided not to after speaking to Gedolim who supported Artscroll .
Rav Aharon Schechter in his long haskama heavily stresses his opinion that Artscroll should only refer to themselves as the Artscroll explanation rather than a translation.Because while an explanation is subject to debate, translation implies that Artscroll is a definitive authority of what the Gemara really means. He felt they should make it clear that they aren't.
In general both the Gedolim on the supporting and opposing side agreed that there is some validity to what other side is saying. Almost none would say it is a good idea for a regular Yeshiva Bocher to learn from an Artscroll Gemara. The Yeshivas of those who wrote haskamas for the Artscroll Gemara for the most part do not have any Artscroll Gemaras themselves.
In the autobiography of Rav Gifter zt"l by Rabbi Yechiel Spiro, (Mesorah Publications - 2011), pp.166-167 it writes about a reception that was held following the publication of Megillas Koheles (the third book of tanach that Artscroll released) where Rav Gifter made a point of meeting the two editors Rav Zlotowitz and Rav Scherman - it writes:
Not only did he offer his encouragement, he even offered to read and comment on manuscripts in progress, which he did for several years. He was truly the father of the Artscroll series, foreseeing its potential when few others did, and providing indispensable support in its fledgling years. At every new initiative, his guidance and public involvement were essential elements of its success, especially regarding the Artscroll/Schottenstein Edition of the Talmud, the impact of which he foresaw from the start.
When Artscroll/Mesorah Publications first undertook the daunting task of translating the Gemara in the Schottenstein Edition of the Talmud, there were those who felt it could not be done properly. As such, there was a disagreement among the giants of Torah Jewry as to whether the project should continue. Rav Elazar Shach, rosh yeshivah of Ponevezh in Israel, was one of those who shared these concerns. But Rav Gifter, who valued Rav Shach's opinion as the authority of the Torah world, campaigned avidly for Rav Shach to allow the project to continue
He felt that he knew American Jewry and understood the importance of such an undertaking. He knew the benefits and understood the concerns. Nevertheless, he felt quite strongly that the project should proceed. Rav Shach acquiesced; he trusted Rav Gifter's insights and perspectives. He had no personal agenda, just the pursuit of kvod haTorah.