** revised again 7/16/15 **
When I tested my battery backup circuit (post 11) I failed to let the systems run on both USB input and battery for long enough. Turns out with 5V/1A input from my USB hub the setup drains the battery. And when that happens the USB output drops to 4.10V. Not nice.
Gory details at http://forums.adafruit.com/viewtopic.php?f=15&t=76014