It may be useful. We have not seen it. For sure, indexing is the driest work that a student can do.
Unfortunately, contrary to what Times reporter Berger was told by the publishers and editors of this new work, there were previously published concordances to the Mishnah and Talmud by Chaim Kasovsky, essentially indexing every word of the texts. We own the four volume Mishnah Concordance and have it open in front of us as we write this. You can order a used set on Amazon as of today.
JVL summarizes the Kasovsky work:
KASOVSKY, CHAYIM YEHOSHUA (1873–1960), Israeli rabbinical scholar. Kasovsky received his early education at the Eẓ Ḥayyim Talmud Torah in Jerusalem where his father Abraham Abele Kasovsky was an instructor. At the age of 20, he was contributing articles to various periodicals on such subjects as Hebrew language and grammar, geometry, and talmudic themes.We do hope the printed edition of the new index gives proper credit in the book to the published Kasovsky work that preceded it.
Kasovsky's reputation rests upon the concordances which he compiled of the Mishnah, the Tosefta, Targum Onkelos, and the Babylonian Talmud (the last of which he was unable to complete). He undertook this task alone and under difficult conditions. He finally evolved a scheme which served as the "key" to the compilation of the concordances. Unable to afford a publisher, Kasovsky acquired a primitive press and set and printed the first volume of the concordance of the Mishnah himself. Its appearance in 1914 caused a sensation in the scholarly world. A committee was established to provide the necessary means to enable Kasovsky to continue his work: the four-volume Oẓar Leshon ha-Mishnah (1957–60); the six-volume Tosefta concordance (1933–61); and the four-volume Onkelos (1933–40). Kasovsky's works subsequently became indispensable to all scholars in those fields. His Talmud concordance (1954– ) consisted of 24 volumes by 1970, up to the letter Mem. After his death, his youngest son Benjamin continued the work (from vol. 10, 1962). His oldest son, Moshe, prepared a concordance of the Jerusalem Talmud under the auspices of the Israel Academy for Sciences and Humanities and the Jewish Theological Seminary of America.
Kasovsky's Tosefta Concordance can be downloaded here - אוצר לשון התוספתא
The other works are out of print or hard to obtain. So we do welcome this new Talmud study tool.
Note that these new index books are not available for ordering on the publisher's web site as of this posting.