Yes and no with the POE. I have seen too many UPSs neglected and not regularly tested or have had the batteries replaced. We had one here last week where they tested a generator, when the power went from mains to generator our main computer room UPS was supposed to pick up the 30 second transfer, well the batteries failed and brought everything down (fortunatly our PBX does not rely on that one
In the aftermath they found a note on the batteries stating they were faulty and needed replacing but no one had acted on it.
What I am saying is, we need to be more diligent with back up systems of all types when moving to a VoIP platform as there will be multiple points of failure instead of one that we will need to stay on top of.