Gartner analyst Ken Dulaney, who is attending I/O, is very impressed with Wave. "This is one of the best product concepts I've seen in the past five years," Dulaney said.

It's clear that Wave represents a significant evolution for Internet communications, particularly e-mail and IM, and Gmail users will in time migrate to Wave, he said.

Makers of competing Webmail and IM services will have to respond with Wave equivalents, or else their users will also switch to the Google product, Dulaney added.