Seriously, this is no joke. As an asset you will be expected to declare a gain or loss on the coins you used to purchase that cup of coffee. The gain or loss with respect to the change of value between the day you received those coins and the day you used them in the purchase.
Very true, no joke at all! That ruling makes Bitcoins far better from a tax standpoint than than USD, although slightly less convenient. Instead of paying your normal income tax rate on BTC, you pay your capital gains rate. Hold them for more than a year, and you have capped your tax rate at half-or-less of your normal income tax rate - 20% max, 15% for all but the 1%, and a whopping 0% for anyone making under $82k. Woo hoo, can I start getting paid in BTC today???
However, in their typical dickish fashion, the IRS has decide to only allow gains, not losses. So if their value goes down, TFB.
That said, you can expect that to change if ever more than a laughably small number of people start filing 400+ page schedule D1s. Make no mistake, the rules for gains on foreign currency (treated specially as something other than assets) exist more for the IRS's convenience than for yours.