As far as I know the only USA sites that have this feature are Pokerstars, Fulltilt, Absolute, and Ultimate Bet (Maybe true poker as well). Carbon and Doyles room have this feature also, but it is not instant.

Pros: it is instant and you can start betting right away.
Cons: You might have miscalculated how much money you have in your account and accidently overdraw. Each time you do this you will owe your bank another 35 or so bucks and plus have a chance of being banned from whatever site you used it on. Anyway, the limits for this purchase method are very small, even after you have done it several times.

The best deposit method I feel is either credit card or signing up with PIC Club so that you can get your money put directly back into your PIC club account.