I've been using iOS 8 on my 5S since it was available.
DO NOT USE A BETA ON A DEVICE WHERE DEPENDABILITY, USABILITY & STABILITY ARE NEEDED!
Here are a list of things that happen regularly with B3-
-Cannot answer the phone, slider won't slide.
-Phone still rings but is on the home screen with no visual indication of a call
-App Store app crashes regularly
-iMessage/Text are wonky. Sometimes everything works, sometimes it does not
-The phone resets itself about 8 times a day.
-Sometimes the screen will not activate. It's black. Takes multiple attempts to get working.
-A few apps do not work, Facebook is not working for me now, Spotify will not work.
-Email app shows email badge but no emails.
-Missed call badge but will not go away.
In short, don't use it as a daily driver if you depend on your phone.