I've recently started to walk more and go to the gym less often. Part of the motivation was hurting my foot (which means I can't do stuff like run on the treadmill) but the larger motivation was that I enjoy walking (whereas I don't really enjoy the gym), I don't get as hungry after (which means I don't overcompensate with too much food), and it's easier to squeeze in (I can do it for 1/2 hour in the morning, without having to drive to the gym).
I am sure I am burning less calories walking than I do, say, running on the treadmill. I still take a few spin classes a week, when I can and I do some yoga at home as well. I am wondering if anyone else walks as their primary way to exercise?