I would have to say that ideallically there are a couple of major hipocracies created by "under God" being a part of the Pledge of Allegience,
"Seperation of church and state" should dictate that the government not mention, endorse, or acknowledge God, a god, or any religious entities.
"Freedom of Religion" ... hmmm ... I've been thinking about this one and there is nothing in the first ammendment that I can recall which states that we have a right to non-belief... thusly a nondescript undefined "under god" may still be justified. As it is only a right to believe in a religion, not disbelieve (I don't have a constitution to look at, so I may be wrong here.)
Like i've said before "One nation under whatever being, idol, God, or lack thereof ..." just isn't catchy
"I pledge allegiance to the flag of the United States of America, and to the republic for which it stands. One nation indivisible with liberty and justice for all."
Just drop the whole mention of under anything. It only sounds weird because we're used to under god, but in three generations they would think it sounded funny with it.