So yesterday I decided to preupgrade fc 15 to 16. And,as always, fedora didn’t disappoint in coming up with issues. Although it downloaded the required packages all fine, on reboot, anaconda fired up and fell through on not being able to install qt-examples, and since it represented a possible media failure from the (local) repo, it decided to fatal error on me, dropping to a non responsive screen.
Fortunately, I could shift to tty2 (Alt+F2) where I got anaconda’s bash. I chrooted to /mnt/sysimg to get to my fedora install, and yum removed qt-examples. This done, I rebooted to find anaconda chugging along fine.
As expected, that wasn’t the end. Since fc16 has implemented grub2 by default, anaconda tried to update grub, but because my Dell Utility partition didn’t leave any space at the beginning of the drive, it failed. So I booted up fc15, which fortunately had not been removed, and gparted the Dell utility partition off. I then made the grub2 config and installed it to /dev/sda. Success!
Not. So, I happily logged in to FC 16, and it was only when I accessed my yum repos, I realized that they were still fc15. After trying yum clean all and makecache, I looked up on the net to find that I needed to reinstall fedora-release. a yum reinstall fedora-release threw up an error "Error: Protected multilib versions: fedora-release-15-3.noarch != fedora-release-16-1.noarch"
After a lot of looking around, realized that the issue lay in the fact that somehow yum was getting $releasever wrong all the time. So, as a workaround, created a releasever file in /etc/yum/vars with 16 in it. Voila!
I then had to erase all the duplicates on my system that amounted to over 5.5 GB(!) using package-cleanup --cleandupes. Additionally, to  avoid dependency hell I had to remove all my boost library installs.

Update: You can follow the rest of the development on this page. I don’t like it.