For the most part my upgrade to FC5 went very well. I spent a lot of time upgrading things I had done incorrectly in the past (like installing Eclipse plugins in the wrong place) and trying to get the Broadcom Linux Driver working w/ WPA, but for the most part everything just worked.
Until I got to work this morning and tried to setup my dual-head mode using xinerama. The external display just wouldn't initialize, and I can't find anything in the logs that might indicate why. I managed to find a thread about problems with FC5 and dual-head on fedoraforum.org that suggested I needed to change my PCI id for the 2nd device, and this kinda-helped but ended up just stretching the single image across both monitors, but still not initializing the external LCD. I looked in the log after this and it indicated it was setting up a MergedFB instead of Xinerama, so I tried setting up MergedFB completely, but it just doesn't render at all. Such are the perils of upgrading shortly after a release.