It is really bad on my 5S, but it mostly just with use. I find it worse on B5 than it was on B4. I even restored B5 just in case, but it didn't help.
It drains about 1-2% per minute when I am using the phone. And that is with the screen as dim as I can still see. The battery usage list isn't terribly helpful, as it usually just lists the apps I have been using.
When I'm not using the phone, the drain isn't bad, especially if it connected to wifi.