Having had past success with yum upgrades for Fedora under the i386 install, I thought I would give it a whirl with my x86_64 installations. The YumUpgradeFaq points out that the yum upgrade process is very straight forward, and this was, indeed, what I followed before.
I ran in to the problem where the elfutils package came up as a conflict, as outlined in the comments here, here (post #5), and here. The last link had a “hackish” way of making it work, but, after some fighting and a little bit of panic, I can say that it doesn’t really work and it just isn’t worth the hassle.
It seems that the only sure-fire way to perform an upgrade would be to use the DVD or CD set to upgrade. Yum still hasn’t caught up to the x86_64 world just yet.
Be aware, though, that an upgrade will take a very long time. Seriously consider the idea of backing up your important configuration files and just performing a clean install.