We are too lazy to paint, so we use unpainted metal miniatures and pre-painted plastic miniatures for every combat.
I've recently come to the realization that my friends and I have turned D&D into more of a skirmish-level tactical wargame than a role-playing game. For us, the role-playing we do in the course of a D&D session is just an excuse to set up a fight. We spend 2/3 of our time maneuvering on the battle grid, 1/6 role-playing, and the remaining 6th is spent BSing or prepping.
A lot of people would like to blame this on third edition, but, to be honest, I'm not sure how new this is. We were doing major battles on battle grids back in 2e, too. Still, part of me longs for more emphasis on role-playing. However, I doubt that things will change too much for my group, because we all enjoy what we are doing, and (as you can tell by our unpainted miniatures) we're probably too lazy as a group to do what it takes to develop a real emphasis on role-playing, anyway.