I never used it, anyway Skype should have a very good suond quality respect to other programs and if you pay you can call all around the world to every kind of phone, with low prices, if i'm right...
Anyway someone is not so sure that Skype is spyware-free...
There are many other programs that haven't the same quality but are more "open": Skype use a proprietary protocol so you can't talk for free to who doesn't have also Skype!
Alternatives could be Ineen, Gizmo Project (wich should have a good audio quality) and VOIPBuster... and many others...
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