One is hard pressed to point to new voice apps, beyond integrated text messaging, find-me, follow-up or visual voice mail, that have become mass market IP voice applications. Dialing from a directory or "click to dial" are helpful, but the bigger changes so far are a simple switch to VoIP in place of plain old telephone service.
The next trend is IP voice on mobile devices, where it has to this point been seen in a "voice from PCs or telephone adapters" scenario.
Contrast that with the pace of development in text-based communications, ranging from text messaging to instant messaging to email to blogging to tweeting. One is tempted to conclude that voice innovation is hampered in part because of its relative complexity, relative incremental cost and an underlying shift in the direction of text communications (messaging) overall.
That isn't to say such voice innovation will not occur; simply that it apparently is harder than innovation in the messaging arena.