Leonardo asks about how much bandwidth does one need for quality VoIP?
Well, I've made a Skype call sitting on the airplane and talking to James Enck of EurtelcoBlog of rather good quality via the Sprint 1xRTT network. The speeds are about 100k down and roughly half of that up. They key though is what happens to the voice packets after it gets on the network.
Beleive it or not, we're really only using about 8-10k of bandwidth. What's really going on is the priortization of packets and the routing that matters.