I voted daily, but I should probably qualify it. If it were TRULY frigid or nasty out – I'm in Chicago, so I'm talking below 0, windy, really bad sleet, etc - I'd probably stay in unless we had to go somewhere. But in general, i try to get her out at least once a day, for a walk, or to do errands (walking), or to the playground or to visit friends - whatever. I think the change of scene is good, and it's good for her to get outside. I bundle her up, put her in the ergo, and if it's really cold, I wear a big enough jacket (like DH"s down jacket) that I can wrap it around both of us. Plus I figure my body warmth keeps her warm. If we stayed inside when it was cold, we'd never get out for a good chunk of the year since Chicago tends to be cold in the winter.
I will say that now that it's colder, I'm looking for more indoor destinations for us. In the summer we took lots of long walks just for the sake of being outside. Now I'm more likely to find a destination - even just the library or the local bookstore or a friend's house - and walk there, then let DD out to play around, rather than spend tons of time outside when it's freezing. I do like giving her a change of scene from our apartment every day, though.