Back on topic.
So is the fring the best software to use if you want a cellular voip program that can call Skype PC users?
Fring piggy-backs totally off the Skype network. It has no major infrastructure to guarrantee you any sort of quality, service or billing structure. You're married then to skype as well as fring.
Truphone, cant be 100% sure - i think their interface (or lack thereof) is pretty wack tho.
yeigo - (and the apparently 'insecure' ComSci grads who started it) wrote their own system. from scratch. it's a world class system, that doesnt have the stresses of 100 000 000 users, the limitation of Yeigo in South Africa is that people like VOX and Telkom - two of the major voip terminators are so backward and inefficient that service can never be truly guarranteed to be 100% flawless. The only other option is to link up with guys like IS but they charge through the ass.
i dont know why everyone is still on about skype, especially in south africa. I have a 1mb home line, that goes straight into verizon (i proudly dont pay telkom a cent at all [directly]) and the voice quality is bloody awful. Skype gonna be a victim of its own success.