2012 35d with only 20k miles. I have the same issue; problem shift out of first to second while giving approx 50-75% throttle with slight uphill gradient. I may call a few Indy shops to see if they have been able to fix this for others. Posted this because it's not the gas, and not just the 2010 4.8

When driving in Colorado with the 4.8i, I eventually realized manually shifting is the way to go.