Powers are the most widely-recognized feature of 4th Edition; the At-Will, Encounter, Daily, Utility structure (AEDU) is both criticized for its “homogenization” of classes (though they each use the structure to do different things) and praised for giving a clear structure to balance their abilities. One Level 3 Encounter Power is, in theory, as good as any other.
Powers are also the biggest challenge for anyone trying to do a clone of 4th edition. Their sheer quantity is overwhelming, and going along with it, the game never really told us how to create our own. (Had the line lasted until a DMG 3, perhaps this would have happened. Perhaps.) It’s something that appears to never have been an exact science- there’s no fixed formula weighing different aspects- but we can both find patterns in the process and hopefully refine it.