Initially I opened and forwarded every port Vonage recommended but have 
pared it back to only 5060–5061 (UDP) and it seems to be working without a 
hitch for the three + weeks that I've had it now, Comcast as the ISP.  In my 
outbound traffic shaping I've given the Vonage adapter high priority.  I 
haven't tried to saturate my upload to see if it helps or not.  Peace of 
mind I guess.