I don't know too much about VoIP but at least with cell phone contracts - I always check the length of the agreement and the overage minute rate because that is where they really hurt - cell phones are truly the way to go as long as you don't give the number to telemarketers. Also watch for hidden stuff - toll fees and additional long distance stuff if you don't get a national plan - I have used some other online phone companies when they were starting out -
www.dialpad.com - very good service.