If your considering getting Voice Over IP there is a free tool you need to try out over at Bandwidth.com. It will list latency of your internet connection, speed and esitmated number of concurrent calls supported. I have FIOS by Verizon at my house which has an advertised speed of 15Mbit down and 2Mbit up. You would think that VoIP would be no problem, but when trying to run the tests, the SIP and MGCP ports came up as blocked, which makes me wonder if Verizon has those ports blocked as well as incoming HTTP and SMTP traffic. I ran the speed test on the website and came back with a estimated 20 supported concurrent phone calls. This warrents further investigation.
Stay tuned...