It is not the best data source or users sample but have a look at
http://mugshot.org/applications
K3b is on the 71 place with 68 users, to put in perspective Firefox is
1st with 4272 and gedit 7th place with 1569.
As David said - 5000 users is hardly representative of overall fedora
users. I use fedora from fc1 and I have never heard of Mugshot - and
how many new users will use it even if they know about it? I guess not
too many - and those who use it will be geeks, not your standard
fedora desktop user.
ps. I just signed up - and I LOVE IT! :) it is the best web 2.0 site I
saw! Great work... and Mugshot app for fedora is also great! Love it
;)