MarkB
Legend
We used to great effect. The dragon they were fighting moved back out of range onto difficult terrain which would have forced the PC's into a bad situation to re-engage. The rogue bravely went forward and slid the dragon right back into melee range of the party. It was pretty impressive.
I was just about to mention difficult terrain myself. One of the great things about forced movement is that it ignores speed penalties for difficult terrain. Aside from bringing a foe across difficult terrain to your allies, as in the above example, you can also push him away through difficult terrain, making it difficult for him to cross back and re-engage.