I'm a frequent switcheroo-er. I find I really have to pay attention to remember what mode I'm in, otherwise I'll walk to the parking garage when my car's not there, or reflexively take the route I use for my bike commute while driving (even though it's inefficient when in a car), etc.

I think the main reason I wear a helmet is that, when it's sitting there on my desk it reminds me that biked into work that day. :-P

And while it is nice sometimes to sit in comfy motorized throne with a good stereo and air-conditioning, I also get those moments when I'm stuck behind a line of cars and all these happy-looking bicyclists are whizzing by me, making me wish I had ridden in today instead.