I can't stand flip-flops. Haven't been able to wear them since I was a kid. I never could understand how other people wear them as just regular shoes. I must have abnormal feet or something.
I generally don't like the hassle of bringing extra shoes. I wear Salomon trail runners unless I'm expecting really bad weather. 99.9999% waterproof (I've never gotten wet feet in them but is anything truly waterproof?). Easy on/off with the speed laces, so if you need to make an 'emergency' run in the middle of the night you can still get out of the tent quickly by just puling them on like a slipper. As comfortable as a pair of tennis shoes. Flexible enough to give decent pedal feel when driving. (I hate driving in boots for this reason). Good traction in messy conditions.
The only thing I would say against the is they don't have stiff soles for carrying heavy packs (but we're not talking about backpacking here) or long hikes on broken rocky terrain - again, not a big issue for most driving trips. Also they aren't particularly warm in serious winter hiking, though I've worn them with snowshoes several times.