The coinbase transaction sends you coins from the network, so this must be reported as income.
When you dispose the coins, you must report capital gains (or loss).
I saw my accountant long ago and discussed Bitcoin at length, and our assumptions based on existing law were pretty much exactly in line with this IRS guidance.
Can you explain to me the logic behind the taxable event of block creation by miners? AFAIK, entities that mine physical gold don't have a taxable event when they pull it from the ground, do they? Isn't the taxable event when they sell the gold?
My rationale is the network of all users paid the coins to you in exchange for you providing a mining service.
Besides I wouldn't risk it on some flimsy interpretation you prefer, because fees and late penalties could be tacked on later. The IRS will always rule for the interpretation that nets them the most tax soonest. Good luck trying to defeat them in tax court.
Btw, I had this interpretation immediately upon learning of Bitcoin. It was obvious to me, well maybe that is because my sister and grandfather were both CPAs, my father is an attorney, and I self-taught myself double-entry cash and accrual accounting and tax accounting (when my sister and grandfather died).