OoC is AWESOME....
....but not as awesome as filling out the rest of the feral tree first. however, the plus side of getting OoC is that you'll grab furor and naturalist on the way, increasing your damage and utility by a significant amount.
personally, if i were to level up another druid today, i would stick my first 13 points into feral, for feral charge, feral swiftness, ferocity, brutal impact and feral instinct. after that, id get 5/5 furor, and then fill out the rest of the feral tree until i hit 50, where i would then respec to pick up mangle. after i grab mangle at 50, id fill out the rest tree to get furor, naturalist, and (at level 61) omen of clarity.
the reason behind this being that, to me anyway, the late feral talents are so strong and synergize so well that it trumps the contribution of omen of clarity at that level. as you get higher up, getting an OoC proc has a greater effect relative to when you were lower, especially given that, by that time, you'll likely have at least a 20% chance to crit in feral forms. on the flip side, when youre lower, your crit chance and your AP are all very low, thus meaning the relative contribution of an OoC proc is less. thus, it would behoove me to fill out feral first.
but as i said, there is benefit to getting OoC sooner rather than later. it really is a personal preference, as you cant deny the power of a free heal at the end of a battle, or the burst damage of an energy-free shred/FB combo.