I've driven auto my whole life, after a horrible learning experience on a manual. Transition to smart's transmission was seamless, except for the 'nodding dog' effect which I solved in my first hour.
I drive in "D" (auto) mode in the mornings when I'm too tired to shift properly. I've found that before 9am I'm more likely to forget I'm in manual mode and rev a cold engine to 5k RPMs and that's not healthy for any engine. So, I go to work in "D" mode most of the time, shift to manual if I need passing speed (pop it left and down once and you can downshift for medium acceleration; in auto mode to downshift you need to floor it, and it will
move).
5mph in a parking lot will drive you batty, though. It's taking me longer to figure out the technique there. Give it some gas and it's fine, let go and in 1st gear it'll slow down pretty quick. Kinda embarrassing when I'm surrounded by pedestrians staring at me, thinking the car's screwed up when it's really the driver. I'm thinking, hey, I slowed down because you stepped in front of me, now please get out of my way. But no, they want to stop and stare in the middle of traffic. Something about pedestrians having the right of way. Pesky laws.