The upgrade from Fedora 14 to 15 on my primary laptop was successful. However, I do not like Gnome Shell. The alternative, Classic Gnome with Compiz, really is the classic desktop. It's not even close. It's about as much like the old desktop as Hawaiian Gardens, CA is a Hawaiin garden. Trust me, I've been there.
I decided to upgrade to Fedora 16 on the older laptop and nearly lost everything. It's a good thing I made a backup before the upgrade. Everything went well until it was time to install the upgraded packages. There must have been a problem with one of the Qt library packages because it failed to install. I restored from backup and tried again, and it failed again. The second time I restored from backup the boot sector didn't get created correctly and grub failed to start up because it couldn't find a file. I restored from backup again but the boot sector still have issues. I did a Google search to find a solution and tried every one I found with no success. I was about to give up when I remembered something from the Microsoft Windows world. When a Windows system is horribly trashed you can re-install the OS and it will only overwrite the boot sector, system binaries, and configuration files. But not all the configuration files. I didn't have a Fedora 15 install disk so I had to download an ISO image on my primary laptop and burn it to disk. I started it up on the older computer and hoped for the best. Luckily there was an option to write a new boot sector based on the targets grub configuration. After that finished I restarted and it worked. I was back in business.
When the laptop rebooted I made a backup of the hard drive and then restored it to make sure it worked. It booted up without a problem. Not the next task was to remove all of the Qt libraries and anything that depended on them. I really wasn't using them so it didn't matter. When I was certain I had removed anything that would break the upgrade, I made yet another backup, this with a different name so I could preserve the older one just in case.
The upgrade went a lot smoother this time. It was still slow because the machine is old but it booted with no problems. I verified that my user directory was still in place and all the files were there, since I needed this computer for an upcoming convention (Gallifrey One). The computer worked flawlessly as the charity auction check-in system.
As a precaution, I've removed all of the Qt libraries on my main laptop so I don't have the same problem as I did before. I never go around to doing the upgrade. Maybe this weekend.