Russell Shaw at zdnet.com has a post in his blog about a new tool from InfoTech designed to allow organizations to calculate the ROI for implementation of a Hosted IP-PBX service (often referred to as IP Centrex) in which the PBX and PSTN gateways are hosted by a service provider rather than owned and operated by the enterprise.
Hosted IP-PBX services make a great deal of sense for small/medium enterprises, and as the services grow in geographic scope and feature sets, will increasingly be attractive to larger enterprises. However enterprises evaluating such services must understand that moving to a hosted model isn't a panacea for VoIP service and support woes. There is still that tricky issue of determining a line of demarcation for support, and how issues on the enterprise local network will be troubleshooted. Users of hosted services will still have to deal with issues such as how to power phones and how to guarantee voice quality within their networks.
Still, as hosted IP-PBX services evolve, it becomes increasingly difficult to build a case as to why an enterprise ought to buy and manage its own phone system when the cost savings of a hosted solution may be difficult to argue against. The growth of the hosted IP-PBX market will certainly put competitive pressure on the vendors of enterprise IP-PBX solutions.