While this is a bit tongue-in-cheek comment, it is true that one of the main problems I had with my Android phone (it was a G1, the first Android phone) was the appallingly short battery life. Even when it was brand new it wasn't uncommon at all to have its battery depleted by midday. After only a year and a half, its battery became completely useless, it dies seconds after disconnecting from the charger.
In contrast, I only have to put my iPhone 4 on the charger every second day at the moment.
counter anecdote, My ~2 week old htc hero hasn't been charged in 34 hours and has 60% battery left. This is with wifi on and mild data-heavy app usage.
In contrast, I only have to put my iPhone 4 on the charger every second day at the moment.