Switch to VOIP

Voice over Internet Protocol (VOIP) has become mainstream. The question today is not whether we should move forward.
It is how are we doing to do this.
Some companies have small offices around Canada and the US, and as far away as China and Russia. VoIP lets them connect to the headquarters easily and cheaply.
When more and more peoples and companies switch to the VOIP, the bigges problems is the network reliability.
For pure data, 10 seconds interrupt is acceptable, because they will re-send the not received data.
The Voip phone conversation will loss the connection and cannot establish it again after 10 seconds stop.

Normally, VoIP users have no complaints about call quality over local area networks, but issues can arise with IP phones on home Internet connections. VoIP security has had relatively little attention so far because there have been no high-profile attacks on VoIP systems, but that will come.
Based on the ITBusiness poll, February 2006.
What do you see as the area most likely to cause problems in a VOIP implementation?
Network readiness: 42%
Network security: 23%
Functionality: 14%
Backup resources: 11%
User resistance: 10%
Even there are some work to be done to improve the VoIP, It is mainstream today.