The coinbase pages seem a bit clunky -- especially not telling you about how many confirmations are needed (apparently 5) -- and showing that 0BTC are present up until that point meaning you have no way of knowing what's happening. Also annoying that the BTC price changed every time I pressed confirm payment again (how am I supposed to know that they payment will fail until it's 5 confirmations?) -- luckily the BTC amount decreased as time went on i.e. what I transferred was enough and that didn't cause any extra failures, but still not too user friendly.