I use the AC adapter as a power supply for my Raspberry Pi (model B) and a
second as a power supply for my Banana Pi.
There, the power supplies are optimally ansich to note, however, that the Pi it then
do not like to have, if you plug in a USB flash drive, then it reboots, because he
Voltage can not maintain, in normal operation (eg Hinterm TV)
extends the power supply but from fully.
For mobile phone: there seem to be problems
For Pi: Actually optimally