The nice thing with POE is you don't need external power for stuff connected at the end point. For example, a wireless AP. Imagine having to put a UPS in the ceiling where the APs are. Instead, the UPS is in the wiring closet and the switch powers the end devices.
IMHO you're still using the same power. Whether it's from the switch or a seperate brick, the device is still using the power it requires.
the next big thing since everything is moving towards 'Green' buildings?
worth it to spend time+energy learning it and try to get a job doing it?
<--- not in computer field
This question is a bit like....
I hear cars are all using fuel injectors. I don't know much about engines, but can I get a job doing fuel injectors?
PoE is a protocol (one of hundreds) that is supported by modern networking architecture. You don't "get a job" in PoE. You can learn the command to enable it as part of a greater knowledge of enterprise switching and routing equipment...
Or you can work handling cabling and running conduit, but the cabling isn't any different for PoE than it is for non-PoE in many circumstances.