I avoid injectors whenever possible. Makes installs of each phone messier with additional cables and it seems like you are always trying to scrounge to find that one additional power outlet under a table or desk and trying to "hide" the power brick. If only a couple of phones, I understand. If 4 or more, just get a PoE switch and save the hassle.

Personally, we've been using Adtran NetVanta switches, and have been very pleased.