My ping to the SIP/RTP server had been under 40ms (one way would be 1/2 that, or 20ms then) and when I used a VoIP adapter I set the buffer to 10ms the minimum. Yet VoIP voice lag was still about 300ms (one way) or about double that of a cell phone. That means VoIP was adding about 270ms somehow, after traversing the internet to the VoIP terminal. Yuck. I never measured with airrave/tmobile but subjectively it felt about the same using the "click test", just call yourself on a landline (so hold one phone up to each ear), and "click"/pop your mouth in one end, and you can get a good feel the lag. If you use google voice try adding that into the mix too for fun, GV adds another 130ms lag on top