There are some applications which don't find a printer service when the client.conf is unavailable (mainly java-apps, for example the Maple frontend). The file can only contain the following: ServerName localhost ... and the apps are happy.
I can confirm that bug. I currently update my network printer configuration and on two machines containing older installs (recently updated, of course) do have client.conf available, but another machine containing a quiet fresh install does not have it. I guess, an older version of cups installed that file and it got never update/overwritten from some point. As the gentoo printer configuration manual refers to that file, I think it's neccessary to fix that bug. Many thanks, Jan
Once read that the client.conf is considered rather deprecated but since I coulnd't find the reference anymore we added it back in one of our recent cups 1.3 bumps for now -> fixed. :)