To summarize, I guess:
(1) Forced Movement is important if there is terrain
Everything from Slow patches to knocking people out of Cover can turn a fight around.
(2) Forced Movement is great with Readied/Delayed Actions
The Fighter with a Readied knock-down power to use on the Brute when he moves adjacent - priceless.
But there is also a third I haven't seen yet:
(3) Forced Movement is important for defensive tactics
The easy way to see this is the "movement-breaks-grabs" effect, but it can also be used to get the Lurker or Brute away from the squishies, to quickly break up a flank, or to let a badly wounded ally make a Double Move (rather than Double Shift) away from a dangerous foe.
It can also be useful on the offense. A Diabolic Grasp that drags the enemy Controller into your front line? Priceless