According to the opinion of the Rebbe the Tzemach Tzedek, and many Acharonim after the Tzemach Tzedek have ruled accordingly, amongst them the Minchas Elazar, the Rebbe of Munkatch, shaving one's beard, even if it is not with a razor, but with Misperayim K'Ein Taar, such as scissors or an electric shaver, one violates and transgresses the Issur DeOraysa, Biblical prohibition, of Lo Yilbash Gever Simlas Isha, not assuming a mode of dress or conduct which is solely reserved for women. Accordingly, one who shaves with any instrument is transgressing a very serious Biblical prohibition.
All the opinions agree that even those who suggest that it is not an Issur DeOraysa and perhaps not even an Issur DeRabbanan, certainly hold that it is not the approach of Yiddishkeit, according to the Derech HaTorah, HaYahadus, the way Torah expects Yidden, Jews, to behave, and therefore one should really have a long, proper, untrimmed beard.