Wizards of the Coast just spat out a pretty decent article on terrain powers, here, a topic near and dear to my heart. I particularly like the guidelines set forth equating various conditions (dazed, blinded, etc.) with the action economy, modified by tier. That's definitely an area that I feel a lot of newer DM's are hesitant and inexperienced with. The only thing that comes to mind that I would have done differently would be to increase the suggested damage range. I feel like terrain powers work best when they're on the side of a little too powerful. You need a good carrot to get the typical risk-averse, closed-box-thinking player to use them. And if they're not using them, what's the point?
The author is a relative unknown, Mark Monack. He has a Wizard Community Blog called Unearthed Wrecana.