This mantra is traditionally called ‘The Mother of the Vedas’.  The practice of this mantra enabled the sages to receive revelation of all other mantras, for this mantra calms mental noise, washes off karmic impurities, purifies the ego, sharpens the intellect, and illuminates the inner being with the light which flows directly from the Source. 
This mantra connects us to the teacher within and helps us receive inner guidance and inner inspiration.  One may not notice an instantaneous transformation, but the effect of this mantra is immense and everlasting.  Gayatri practice is more suitable to those who may be struggling with confusion, doubt, skepticism, lack of self-trust, and lack of direction.  It is good for those who are tired of trying this and that; for those who want to get in touch with their own intuition rather than leaning on external aids (i.e. friends, teachers, books etc.)