Here's a quick example where things are made easier.
# finds, updates and saves car objects
$mapper = new CarMapper;
#find a car
$car = $mapper->findById(45);
#set the driver of the car, a driver object
#save the modified car
Of course there are lots of lines of code hidden away which implement the functionality, but we used 4 lines of code there to find a car, change it, and save it.
Powerful stuff, and much easier to read too.