The I AM mantra is similar to OM, but not exactly the same, so the effects are somewhat different. I AM has both linear and circular qualities contained within it, while OM is circular.
OM is mother. But where is father? As we become enlightened, a divine romance occurs in us, a joining. In the I AM mantra, "I" is the father vibration, and "AM" is the mother vibration. Recall that yoga means "to join." This happens on many levels in many ways.