I think it depends how much you push off with your calves, too, but yes, they get a good workout. But along with hams, you should do exercises to strengthen your shins and protect them from injury. Otherwise, you will end up with a stress fracture like me! You can easily do this by leaning against a wall (feet 1 foot from wall, shoulders leaning against it) and flexing your feet up towards your shins. Also focus on running heel to toe.
To strengthen hams other than standard machines, squats, walking lunges, etc., I use the stair-stepper to kick my leg up and back (toe facing floor) to build upper and mid hamstrings. I'll also take time in my interval workouts to do "exaggerated" running styles, like trying to kick my butt and running with really high knees in front. This will help with the balance.