Towelroot will only work if your write protection to the sys partion is turned off. It will most likely never work on stock b/c of this write protection unless geohot can somehow bypass it.
HTC One M8 running stock(current)
SGS III running Quantum by pwncakes (old)
Moto Atrix 4g running Neutrino(older)
Samy Captivate (paperweight