If the system has a lot of fonts then it can take a long time to scan these, and we generally cannot use the system font cache so this scan has to be done for each user. The end result is that the first login for every user takes quite some time (40 seconds has been observed).
Debian and Ubuntu seems to have very large default font sets, whilst Fedora is more conservative (6-8 seconds scan time).
We added a progress dialog in bug 7159 to give the user some feedback, but the delay is still very annoying.
Perhaps we can have our own system wide cache? The problem then becomes how to maintain it to make sure it stays up to date.
See also bug 7170 which has the corresponding issue for the server.
(In reply to comment #1)
> See also bug 7170 which has the corresponding issue for the server.
for the client*