Asia, meanwhile, lags behind. China restricts VoIP as a way to protect its big telcos, but expect that to change.
For the moment, Vonage is the market leader in the US. But cable companies are weighing in big time, and Vonage's days are most likely numbered.
The same holds true for traditional phone service. Telcos are going IP, cable services that provide phone service are going IP, and Skype has big-time numbers as well.
Whether you use VoIP now or not, at some point you will. It's the wave of the future, and old-time telephony will soon be gone.