one of the biggest mistakes I see small businesses make while migrating to a voip solution is that they totally forget about the access or try to save money on the access. They run it over some residential internet product or basic business internet with no SLA and no redundancy. When it goes kaput they claim that voip is "unreliable". If you are serious about going voip then you need a redundant connection from 2 different providers. You may have the fanciest hosted solution but if you can not reach it then you are hosed.