I had a bad experience upgrading F-14/KDE to F-15.
I upgraded from the F-15 DVD ISO, by NFS from another machine, after abstracting isolinux/vmlinuz and isolinux/initrd.img and transferring them to /boot on the target machine, a Thinkpad T43, and writing a trivial stanza in /etc/grub.conf on this machine ---------------------------------- Fedora-15 install root (hd0,2) kernel /boot/vmlinuz askmethod initrd /boot/initrd.img ----------------------------------
On re-booting into this, all went well; the ISO was found, and after choosing to upgrade the F-14 system about 1,600 packages were updated remarkably quickly - about an hour.
But then when I re-booted my problems began. Firstly, the screen was so bright I was frightened something might blow. There were random colours and broken images on the screen, and finally I got the error message ---------------------------------- Failed to connect to X Server.pdate pf Smolt.... PC/SC.... devices..ee 'systemct; status kdump/service' for details. ----------------------------------
I found that Alt-F2 gave me a text login, so I edited the stanza in /etc/grub.conf created by the installation, replacing "rhgb quiet" in the kernel line by "text".
Now when I re-booted I got a text login. On running "sudo yum update", I was told there were 1.1GB worth of packages to update. The update failed with a number of errors, which I did not pursue. I guess I should have run "sudo yum --skip-broken update". Instead I updated in a number of steps, like "sudo yum update k*". This seemed to avoid most of the errors; the only recurring problem was with gthumb, which I yum-removed and later re-installed.
After this I ran "startx" and a KDE screen came up. So I deleted the "text" in the grub kernel line, and re-booted.
This brought up a proper KDE screen, but several of the KDE programs ran strangely. In particular, on choosing konsole from the f-menu a page-size window opened, and then shrank rapidly until it was about 3 lines deep, and a quarter of the screen wide. (I've never seen this before.) On enlarging the window by moving the mouse on the perimeter, I found that I could not input into the window.
Finally, I deleted ~/.kde and started again, and at last I got a proper Fedora/KDE setup.