The strongest argument in favor of Bitcoin compared to precious metals is Executive Order 6102: http://en.wikipedia.org/wiki/Executive_Order_6102
A hybrid approach might make sense until the Bitcoin network has a longer track record.
A private gold storage company, established in a safe jurisdiction, could accept Bitcoins for gold and redeem gold for Bitcoins. Unfortunately you would lose the advantages of Bitcoin’s low holding cost and some of the safety from sovereign seizure.
But what you gain would be reduced exposure to the long term risk of Bitcoins losing value and you would still be able to access your money quickly in a bank-free form that trades more easily than gold certificates from a private reserve.
The challenge is to create a system that is immune from the risk of the exchange absconding with the gold (e.g. e-Gold). Ideally there would be a way to trust the exchange that does not depend on recourse to the legal system. No obvious way comes to mind.