The same would be true for ANY currency you weren't already holding. You'd face the issue of conversion and the timing of transfers/wires not meeting your "penny more / penny less" test.

For example, my US bank wont send rubles to my account in Russia. When I want to send funds, they send USD to the Russian bank, which can take a day or so to happen, then the Russian bank converts the dollars to rubles at whatever the exchange rate is at that time and credits my ruble account.

Granted the delays in getting larger sums from Coinbase and the volatility in btc are higher in the btc case, but the basic problem is the same. The key difference with btc is that the actual transfer happens MUCH faster than with legacy banking system.

You might consider buying a small surplus of coins from coinbase and holding them in your own wallet, then once you posses them, contact the party you want to pay and agree on a USD/BTC price, and hit send.  For a little more effort, you gain much more control and faster transfers.