I'm using Iburst and have been trying out various voip programs to find an alternative to Telkom. Voipdiscount.com is proving a total disaster as a pc-based phone, but the ones that work for me are Skype and Gizmo Project. The latter is similar to Skype and a touch more expensive, but I think that with Iburst Gizmo Project gives slightly better sound quality than Skype.