Palamida has been tracking the movement of open-source projects from GPLv2 to GPLv3 and estimates that 119 projects have converted (to GPL/LGPLv3), which represents less than 1 percent of projects using the General Public License, or GPL. Nothing to write home about, in other words.
Why is the uptake so tepid? Well, the rampant FUD around version 3 probably helped, but I don't think that's the main issue. I actually think the primary problem is that GPLv3 didn't go far enough, in many ways. It's an updated version of GPLv2, which is good, but it doesn't resolve some of the industry's most pressing issues, like the ASP loophole.
Instead, it tackles DRM (digital rights management), TiVo and other such issues that are salient to the Free Software Foundation but not so much to most of us.
Still, it's a good license, and I think the adoption will continue and accelerate as people grok it better. I particularly think that it will find adherents in companies and communities that have used quasi-open-source licenses. It allows for reasonable attribution, for one thing, which may serve to obviate the whole debate over Mozilla Public License (MPL) plus attribution.