I'm in Shutter Priority mostly, as my subject matter is often fast trains and I don't often get a second chance if I mess up a shot. I do some PP, but try to limit it. With trains, I'm trying to capture reality as seen through the lens and pay close attention to light and composition. It's a habit that's hard to reverse after shooting film for 40 years.
When in an artistic mood, I'm in Aperture Priority to work DOF. The only time I'm in Auto is for quick snapshots, especially with a flash.
After 4-1/2 Years, I still love my D-5100 and am still discovering new things about it.