According to this article, Fedora has somewhere around 9.5 million users. That put’s it 1.5 million above Ubuntu, who’s claimed user base is at around 8 million people.
The way the Fedora project tallies it’s users is apparently through IP addresses gathered during updates. The article notes that it can be flawed… in which it might very well be. I believe that tallying the total number of users is difficult, if possible at best. For example, I use Ubuntu, but I also have a Fedora computer sitting on my desk. I also do not run into too many users, who are Linux users, that run Fedora. I know of several, but most Linux users I know run a version of Ubuntu (or a derivative).
Paul Frields, the project manager of Fedora, took a moment to rip Ubuntu for not disclosing where it gets the stats for it’s user base. However, it has been disclosed, although the process is not as open as Fedora’s own.
Either way, even if Fedora does have 9.5 million users (or more), it can only be a good thing for Linux.