If power creeps turn out to be more of an augmentation than a real game-changer, then I think they'll make for an interesting dynamic. It's reassuring to hear that they won't disturb the gameplay balance too much.
But when it comes to the discussion of leveling the playing field for newer players vs. players that have been building an empire (and an advanced code base!), I think achievements might play into the solution. For newer players, achievements could come with rewards, bonuses, or resources that could help them establish themselves. I really don't want to see Screeps turn into some generic MMO, but ideas borrowed from other games might include power-ups like 24 or 48 hours of decreased spawn time or decreased spawn energy requirements, or an achievement that rewards a player with 100k energy- rewards that would be trivial for well established players, but could really support novice players.
Also, is there any collection of information that is established to help support novice players? I know some of us have public code bases (myself included) that have been forked by novice players, but a repository of information might be good as well. Just a thought.