Mine's between 25-50% during the day depending on the brightness of the room. I don't use it much outside so can't say.
One complaint I have with the 5 is that it doesn't go dark enough for when I want to read in bed - 0% is still too bright!
My wife likes to have her iPad 3 at 100% brightness nearly all the time, even inside. Whenever I pick it up I feel like my eyes are gonna burn! Luckily it's a quick shortcut to change the brightness on the iPad.
Another complaint: the fast app switch on the iPhone when swiping left to right has volume slider. Why? I have volume buttons on the side! Why can't it be a brightness slider, like the iPad has!
I agree with the 0%. The brightness should have a wider range with 0% being a LOT dimmer for night reading. For all iOS devices and Macs. I mean, nothing to lose lol.