Recently dropped cable and went with an indoor antenna. I live in an area where over the air TV reception is great, and getting network and PBS on HD is a breeze. As others have noted, this part is probably the diciest because not everyone gets great reception, and not everyone is satisfied with the over the air offerings (i.e., live sports, cable-only programming).
I supplement with Netflix and ESPN3. It's not the same as cable TV, but, my wallet says "thanks" every month.