You've lost me. Why would a consumer ever bother with BTC? Especially if both ends of the transaction are paying fees, spreads and paying for an escrow service.

Also, does the merchant set your prices in BTC, and change prices a few times per week as the exchange rate fluctuates? Or are the prices in USD?

Who said anything about an escrow service? One of the whole reasons to use BTC is irreversibility. You can build a crowdfunding site on atomic USD->BTC->USD transfers, precisely because there's no possibility of chargebacks. Crowdfunding is fundamentally a "pay cash in advance for some probability of a return" model, and BTC is the "cash" part that would make that work. Credit cards are very bad at being cash.

Before my transfer agent will send the irreversible transfer of bitcoins, they'll want to receive their USD by some irreversible means.

Why bother with the bitcoin sandwich? Why not transfer between the agents using Western Union or Hawala or whatever?

That's interesting! But isn't there any delay between currency exchange and an exchange fee as well?

Yes, I imagine that, like with Paypal, the sender would be responsible for eating both exchange fees. The delay, on the other hand, would impose price volatility that would likely be equal in both directions--so as long as the transfer-agents formed a network with an agreement that the receiving agent smoothed over both all losses and all gains during transfer, there should be net zero liability (they'd just need some float.)