My son went to Head Start four days a week last year, and he loved that the bus picked him up and dropped him off at home. I was nervous at first, because I never really let him (at that time) go anywhere without me... but over time, I appreciated the fact that I didn't have to wake my new baby up to take him to school.
My son's daycare has 2 vans, but I think it's just to pick the school kids up and to take the older kids on field trips. I think they can also use it to pick the 3 year olds up from Head Start, but I'm not sure.
Either way, I wouldn't use it. I don't want anyone but DH or I to drive our kid anywhere.