Well I've gone around in circles with Vonage, love it, then wow it sounds bad. I mean, I can program how many rings to try before forwarding to my cellphone? That's cool. But I can't hear what other people are saying on a conference call? That's really not cool.
I measured latency at about 250ms above a normal phone line (that's about a quarter-second), and after enough choppy conference calls, it only made sense to be done with Vonage.
I have a 1.1mbit SDSL, which is way above their minimum configuration (128kbit). I'm only a couple hops from Level3's backbone in LA. My ping to Google is 20ms. This all should be adequate, so I didn't spend time trying to figure out why it's broken. This stuff's really gotta be plug-and-play.
I really wanted this to work -- the features are amazing and so is the price, but I guess in the end you get what you pay for.