It's "CALLcentric", not "CONcentric".
And, no, nobody in their right mind should ever use Future9 or VestaLink for anything remotely business related. Some people have the naive idea that buying something like this from a "small businessman" is somehow better than buying from a company with high-quality carrier and network connectivity, support staff, and business scale. It's seen as a "rage against the machine of big business." They're blinded by that misguided belief, into ignoring service outages, service quality problems, lack of support by more than one guy, and an overall amateur service. If any of those issues were pervasive at a larger provider, people would be flooding the forums with angry tirades.
Buy your coffee from a small, local roaster instead of Starbucks. Shop locally and support your local businesses. But buying reliable, consistent telephone service from a one-man show is just plain foolhardy.