Also remember that Prone and Difficult Terrain interact in a very nice way. If you're prone, you have to spend an action to stand. If you've already spent your move action to stand, and nobody is within melee reach, the only way you can attack is to use a ranged attack, or to charge. You can't charge across difficult terrain. This spell probably laid down difficult terrain in between you and your intended charge target.
So aimed right, it can deny your opponents a turn.
You can charge across difficult terrain in 4e. It just costs extra movement as normal. (This is mentioned in the charge action in the PHB.)