Fred and I both came to the conclusion that today, most enterprise end users still view UC as a "nice to have," in contrast to the first-generation IPT. Fred recalled that once the vendors stopped doing R&D and product development around TDM, the enterprise manager's hand was forced: If you needed to add voice capability, whether in a new location or as part of an expansion, it was absolutely imperative that you come to grips with VOIP. Maybe you wound up going TDM (remember, shipments didn't cross the 50% line until a couple of years ago), or you went hybrid or IP-enabled, but if you didn't know how IP-telephony worked and how to make it work, you were putting a mission-critical part of your business IT infrastructure at risk.
I think we underestimate the magnitude of that change because the end results have been, in most cases, rather underwhelming. You went to all this trouble (and expense!) to migrate to a platform that basically did what your old platform--which you hadn't had to worry much about for a decade or more--did. So in hindsight, or what's nearing hindsight for many people, it doesn't necessarily seem like such a big deal.
In contrast, UC holds out a lot of promise for some much more significant benefits. But those benefits involve changing how you do business, which may be an opportunity but also necessarily involves costs, too, and which potentially might not pan out at all. The motivation for changing is counterbalanced by the motivation to more or less stand pat, or at least to change at an extremely attenuated pace.
There may emerge a forcing factor in UC; I can't predict what it is, and I haven't heard a prediction from anyone else that made a lot of sense.
In the meantime, there is a strong sense of urgency on the part of the vendors in the UC marketplace, but that owes itself almost entirely to the emergence of Microsoft and IBM as competitors in this area. I might add that enterprise communications professionals are also showing a strong interest in learning about UC, as we see in VoiceCon attendance and signups for webinars, road shows, pretty much anything we do that's got "Unified Communications" in its name.
UC's time is coming, and I think this interest we're seeing shows that buyers want to be ready. But they're not sold yet.