It would appear that efforts to address problems of compatability and interoperability between the various VoIP protocols, packages and services are making some headway.
For users - and especially small businesses - the issue has been of growing concern as the popularity of VoIP has led to a huge increase in the number of VoIP services.

A growing number of UK broadband users plan to start using VoIP in their homes, according to research.
The study by consultancy Booz and Company found that 44 per cent of consumers plan to use VoIP in the next six months.