OK, i've had vonage now for 6 months and Packet8 for 2 months (vonage for my office, packet8 for my home).
all other things being equal Vonage is WAAY WAAYY better than packet8. i don't think that packet8 is worth the $20.00 a month. matter of fact, i'm going to cancel my packet8 account and go with Verizon.
i've been VERY VERY disappointed with packet8. Vonage has been pretty consistent.
I think it's the VOIP Routers they use. Vonage Uses the Cisco router and i dont' remember which one packet8 uses but it seems to drop more calls, get's more busy signals WHEN THE OTHER LINE ISN'T busy (i think that's a packet8 server problem).
bottom line, don't be tempted by packet8's price. Vonage is the better way to go.