It actually depends on where you live, your specific situation.
For the most part, 2WD works just fine in Wyoming, and I can easily drive from our house back and forth to Cody, and all over the place. However the last bit by our house, going uphill on gravel with packed snow, I've often wished I had 4WD. But I never wished for it enough to actually go out and buy one. Instead, on those days I can't drive up to the house, I just park on the highway and walk up. It's usually a nice walk. Now, that wouldn't be viable if the walk was a couple miles rather than a couple of tenths of a mile.
One pattern I've seen over and over is that it's clear sailing on the highways, packed snow in town. In town there is more traffic and when it snows it immediately gets packed down, while out of town the wind more easily blows the snow off the road.
I wouldn't buy 4WD unless I tried going without it for a while, where I was going to live. Unless you really just like having it, which is a different thing.
<later> Sheesh, I see I already posted on this one. I need to pay attention more...