One thing you do not have to worry about while using the iPhone camera is the short battery life comparable to some digital camera batteries. the iPhone has a great battery that can easily give the user a full day of heavy use.
Forget about carrying a charger or extra batteries. The iPhone is one of the best devices for battery use. If you are an extra heavy user there are some portable battery chargers that can extend your shooting session.
The old saying is the best camera is the one you have with you. That has never been more true since the addition of a quality camera for the iPhone. More people are taking more photos because they have their camera with them at all times.