I have no personal experience of doing this, other than to help out a colleague when their car has broken down and back during the fuel shortage going back a good few years. However, we live about 15 minutes away from a junction of a major motorway, and every day there are cars parked down the side of the road from people who lift share.
Clearly for them it works, and common sense would say to me that not only would it save money and be greener for the planet, but could well introduce you to a whole new lot of friends. I think from me, as a 'Lift share virgin' it would get the thumbs up.