I like
Skype - especially because Skype has Linux Clients, and they simply work, unlike Google Talk, Y messenger etc, on Linux. (In case you're interested to run Skype client on Linux, go for the latest Linux Beta Clients from
this page)
But, what is preventing me from using Skype as my long distance/International Call Carrier?
Their
rates, of course...!
Rates to India from
Skype -
15.0 ¢ per minute
Rates to India from
elsewhere -
6.2 ¢ per minute
Do the math...!
Skype rates:

Calling Card Rates: