I've had it a week and so far it's been perfect - quality crystal clear.
It is voip but calls are not routed over the internet, so quality is more assured - ie I think the voip part just runs on their network and then directly interfaces to a pstn.
They only published s for ireland and uk. Be interested to see what international calls cost.
The install just involves replacing your cable modem. I bought a set of cordless dect phones as you have to plug your telephone into your cable modem. So I just plugged the dect base station into the cabe modem and have multiple phones around the house but only needed one phone socket.