This might seem an outdated question to some. After all, the communications market is well past the threshold where more than 50% of telephony lines shipped are IP-based lines. But it's still relevant to the vast numbers of organizations still running TDM-based systems for their day-to-day communications. Reed Smith LLP, a global law firm, must have asked themselves this question at some point -- read about Reed Smith's rationale for migrating to IP.
Why are you moving to IP-based communications? Or, equally interesting, why are you not?