I think the best tests of a battery are real-world ones. Rob Pegoraro tested his iPhone 5 in everyday life and found that it matches up great with competitors. My favorite quote:
"Each figure beats any Android phone I've tested on an LTE signal, although some 3G models have done better."
In other words, the iPhone 5 is a great LTE phone in particular. Pegoraro found he didn't have to charge his phone until into the night, although he's yet to fully test it at a mobile-heavy event like SXSW or CES. I find that when the phone has to strain for signal it drains the battery faster, so we'll have to see how that goes.
Still, the iPhone 5 battery, in such a small space, is a wonder to behold.