According to two employees at the Sprint store, using an unofficial charger for the Galaxy S4 will negatively impact the overall life of the phone's battery (edit: in other words, the battery will need to be replaced much sooner than if one always uses the official charger).
I've never heard this before. Does anyone else know what they are talking about? What is special about the S4 charger? I saw someone online mention that a "special code" is transmitted over the USB connector, which the phone will use to judge if it is an official charger; again, new to me, but I'm not a hardware expert.
Update: I still haven't figured out an answer to this. Regarding the "special code", the post I saw may have been referring to the IC chip, but I don't know. So if we look at the distinguishing characteristics of a Micro USB Charger, there's 1) whether it has the IC Chip; 2) whether it is 2 amp vs. 1 amp; anything else?