Q. Should a Bar Mitzva bochur say shecheyanu on his new tefilin, if not for the mitzvah at least for the great pleasure of having new tefilin? Why should tefilin be less than a new suit?

A. Lehoros Nossan (2: 9: 9) quotes Ridbaz that indeed one recites sheheyanu on new tefilin, as he would do on new utensils when he derives pleasure from their acquisition. However he also quotes Avudraham (sha’ar 3) that one only recites this brocho on items that provide physical pleasure. Mitzvos, similar to tefilin that don’t provide any “hanoas haguf” one does not recite sheheyanu. Others (Be’er Eliahu O.H. 53 et. al.) mention that one does not recite this brocho on utensils made of leather, since they involve the death of Hashem’s creatures.. Mogen Avrohom (223: 5) rules not to recite on new seforim, since mitzvos were not given to us for material pleasure. However Mishna Berura (ibid.) quotes Chayei Odom who opines that if someone acquires a sefer he greatly desired and rejoices greatly having it, he should recite, therefore, one should not protest against the ones who do recite. Birur Halocho (O.H. 22) cites contemporary teshuvos such as Beis Hayotzer (4), Chino Dechaye (49), K’naf Renonoh (O.H. 17, Zichron Yehuda, et. al.) that maintain one may recite sheheyanu the first time one dons a new pair of tefiln.
Horav Shlomo Miller’s Shlit”a opinion is that the accepted and widespread minhag is not to recite sheheyanu.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a