I hate it when RPGs pull the "enemies level up with your character" crap. I hated it in Oblivion. It was tolerable in Skyrim because it was less obvious, and done in a crafty way. I'm not quite sure how extensive it is in Diablo 3 yet, I just happened to notice it in the patch notes.
I understand that, conceptually, there's no reason the player character should be the only person in the entire world looking to improve themselves. Maybe the enemies do practice their shit while you're off on the other side of the world doing something else. It's not unreasonable.
But your ability to annihilate or get annihilated by various enemies in an RPG is essentially the only benchmark we really have for character strength. It's the only thing that provides context to all the number stacking we're doing otherwise. There's no point in spending hours and hours getting your character all decked out, tripping balls with particle effects and swinging a god-sized sword if you can't walk into a group of low level creatures and handily decimate them.
It's easy game design, sure. "Uh, wherever you go, the enemies will be challenging." Blam. With some simple scaling code, the developer has ensured that one-hundred percent of their game will be useable content. You won't miss out, or outlevel some content because you were off doing content elsewhere. It's all relevant all the time. It makes sense on paper.
I just feel like it turns a game into a treadmill, doing all the work but essentially getting nowhere. I'd prefer go for a real run, and end up somewhere different from where I started, I guess.