Starting in iPhone OS 3.1 (I think), the battery charging indicator on the home screen has been moved down. It was most likely shifted so the iPod controls no longer obscure the battery icon when you double tap the home button.
That seems to be the idea, anyway. The thing is, when the iPod controls are hidden, it looks really off center. Distractingly off center. And it wasn’t exactly obscuring anything before — it was transparent.