My experience with Fedora 15 was not as I had hoped. The ATI graphics driver was particularly problematic (regular minute-long hangs due to spinlock issues) so I decided to try a completely different distribution. I decided to go with Kubuntu 11.04 and performance has been excellent.
While the install went OK, I am not (yet) convinced it was worth the hassle. While it’s nice to pick up bug fixes, I haven’t noticed much change to the feature set.
In summary, while FC8 and FC11 worked out of the box, FC12 failed to provide me with sound. I discovered later that the KDE mixer had set the center volume to mute. Once I unset that, I had sound.
Other than that, it worked pretty well.