I've spent a year and a half driving a manual transmission as my daily drive.
The different behavior of a manual-transmission car became a deeply-ingrained habit in my mind. When I took a corporate test-vehicle home over the weekend, I was a little surprised when the automatic-transmission vehicle started moving the moment I let off the brakes.
I also noticed how the fuel economy gauge on the dashboard behaved. A very shallow up-slope (I think less than 1% grade, but over two miles) caused the fuel economy to drop noticeably. I could have maintained high economy, but only by coasting and losing lots of speed. Steady speed on a similar down-slope, or a flat section of roads, showed the maximum possible reading for fuel economy.