Everybody should use them. It takes the stress away from ringing phones and the panic to answer.
Nevertheless, even thought it is illegal I still see to many people talking on their cell phones.
Some sober thoughts on the issue from Wikipedia
As a percentage of distraction-related accidents
In September 2010, the U.S. National Highway Traffic Safety Administration (NHTSA) released a report on distracted driving fatalities for 2009. The NHTSA considers distracted driving to include some of the following as distractions: other occupants in the car, eating, drinking, smoking, adjusting radio, adjusting environmental control, reaching for object in car, and cell phone use. In 2009 in the U.S. there was a reported 5,474 people killed by distracted drivers. Of those 995 were considered to be killed by drivers distracted by cell phones. The report doesn't state whether this under or over represents the level of cell phone use amongst drivers, and whether there is a causal relationship.