BW blog has a blog on how VOIP is not the cheapest option for calling international. However, I feel that going VOIP is not just about international calls, it provides more options for the same buck(s). I just got a mailer from AT&T saying that their prices for calling features would increase, Call waiting would cost $4 (3.43 currently) and caller ID would cost $8 from $6.17 ( I dont know how their cost increased, thats why I call it rip off).
With all necessary features, your traditional telco bill would run into $40, with VOIP phone for ~ $25 you’ll get all those features and unlimited domestic calling. Only thing is the long term reliability and financial health of the VOIP providers. I have talked about the advantages of using VOIP to India calls in my other posts here and here. Also, I feel that calling cards are not reliable and have their own issues.