We live in suburbia with good public transport links -- no kids, no car. So far, we've been alright without one, but we're considering buying one before the end of the year. I've always said I won't have a kid unless I have a car -- I'm not one for trying to get the buggy on and off the bus and using the lifts at the Metro stations, etc. Overall, a car isn't a necessity -- our groceries are delivered, etc., so we've never felt at a loss because we don't drive. We're hoping to buy a house in the next year or so, and that might really influence whether or not we buy a car -- we don't want to be limited to houses near a bus stop, etc.
At this point, if we got a car now, we'd only use it on the weekends if we were travelling and for those occasions when we want to buy something heavy and don't want to have to arrange a delivery. Otherwise, it's pointless -- a bus or Metro pass is much cheaper than petrol!