1. Chasam Sofer - Calm acceptance. At first glance. this would seem to be a bit surprising given that the Chasam Sofer was 1- a student of the R' Nosson Adler and R' Pinchas Horowitz who were both Mekubbalim, and 2- seems to have been an adherent of Kabbalah himself (See Marc Shapiro's article in Be'erot Yitzchok - Aspects..). In truth, Yavetz's claim was not all that radical since R' Chaim Vital (I don't know the exact source) had already suggested that there were interpolations in the Zohar. Moreover, the question in this case was not the authenticity of Kabbalah as a whole since that was supported by the Ramban, Sefer Yetzirah , etc. but of one (admittedly very important) source of Kabbalistic teachings.
2. Chida - Denial. See the citation in the link in note one and the discussion there.
3. Ben Ish Chai - Grudging acceptance - In the Kuntres Sod LaYesharim that is at the back of ShuT Rav Paolim (I don't have the sefer in front of me, I will try to bring the exact Siman later) there is a discussion concerning a Teshuva attributed to the Ari printed in Avkas Rochel 136. The Ben Ish Chai insists that this letter is a forgery (the Teshuva would appear to show a very weak understanding in the subject and the Beis Yosef's response is very critical) and grudgingly cites MS as proof. The Ben Ish Chai was clearly very upset at the Yavetz for writing MS and I believe that the sharp criticism of Yavetz in the introduction to Ravv Paolim is hinting at this.
4. R' Moshe Kunitz - Apologetics - Kunitz's book Bar Yochai (available at Hebrewbooks.org ). The book is full of rather ridiculous nonesensical interpretations and was never taken very seriously. Shir (I intend to continue posting on him as soon as I have time) was enraged by this book and wrote very sharp criticisms inside his copy of Bar Yochai. These notes were published posthumously as a pamphlet - Maaneh La'Mitpachat. From the notes it appears that Shir was chiefly angered at the insulting tone with which Kunitz responded to the Yavetz. It is possible that Shir also wrote this becuase he was upset at Kuniz's involvement with Choriner (whom he detested - see Igrot Shir, and because Shir was very much against even the slightest change in practice - see his letter regarding kitniyos cited in Zecher Yosef OC V. 3), and because Shir strongly believed that the Zohar was forged by R' Moses De Leon (this is apparent in either the first or second of the letters in Igrot Shir. Shir wanted to examine R' De Leon's other seforim so he could ascertain this.)
5. The Gra - Oblivious? - The most puzzling reaction is that of the Gra - namely no reaction. The Gra had a tremendous critical sense (See L. Ginzberg , Students.., I. H. Weiss frequently emphasized that the Gra was the founder of the science of criticism,etc.,etc.). Although the Gra's form of criticism was rather different then that engaged in by the Yavetz, it is still strange that he didn't at least respond to the Yavetz's critcism. I emailed Prof. Etkes thinking that perhaps there might be some hint of a response in the Gra's kabbalistic works but he assures me that the Gra had absolutely no doubts regarding the absolute authenticity and authority of Kabbalah.
(One final note, the Torah Temimah very pointedly lists Eish Nogeh (the Yavetz pointed out that this seems to be based on the Portugese Esnoga - Synagogue) in his list of terms for synagagogues in Mekor Baruch - Mevo. See there - I think he is trying to hint at some type of response to this criticism of the Yavetz.)
 See here for an interesting discussion on Mitpachat and the Yavetz as well as some more sources Re: the CS and MS. He was accused of being a Reformer because he wrote a responsum in Nogeh Tsedek permitting the introduction of the Organ in the Synagague. This seems to have been a mistake on Kunitz's part and he is not to be considered a reformer.