I mostly drive my car in D mode, but living in Colorado with the Rockies, I love having the option to go into M mode and holding the gear that I want for decents. And the car seems a bit more responsive when in M mode. If I'm feeling frisky I'll nail it in M and let the gearbox make that first shift from 1st to 2nd and then I take it from there. The car jumps a bit harder that way.
Otherwise I'm usually in D and cruising along. I forget to shift sometimes in M mode. Gotten lazy I guess. I used to only have manual tranny cars for a long time. Maybe I'm also turning into my dad. Hmmmmmm...
I like my Paddle Shifters!