How bad is the iPhone 5 battery?

I was the proud owner of the Samsung Galaxy S3, and I still own it, but I'm no longer proud. Samsung's OS tweaks completely ruin the experience and Android still has app quality problems, compared to iOS. I like the UI of stock android, but I don't think i can use an OS that just doesn't have the support of iOS. And since I have the international S3, there is no stable ROM other than TouchWiz. Ugh.

So I want to get an iPhone.

I don't really want to wait for the 5S, but I am worried about the iPhone 5's battery.

Is it better than that of an S3? I've had amazing battery life with CM10.1 on the S3, and average battery on stock Wiz, but all I hear is that the battery of the iPhone 5 is annoying.

I don't make many calls, and I barely use it during the day, only in the morning and at night. Is the iPhone 5 really horrible, or is this just major power users.