I agree, for one of the functions of the hamstrings (bending the knee), there's not much (at least in a home environment) that can beat hamstring work on the stability ball. And it's easy to increase the intensity by adding roll-ins and by raising one leg, or even holding weights on the hips (if you ever get to the point where doing the one-legged version becomes "easy"!)
For the second function of the hamstrings (helping to raise the body from a bent-over position to straight), deadlifts are excellent.
Step-ups also work the hamstrings nicely.
PLB includes all three of these exercises, so I would have to consider it the best hamstring workout of Cathe's (unless I'm forgetting another one that combines all three of these).