1. I'm currently running Fedora 9 using Livna nvidia drivers and my games work all right. (etqw) KDE's desktop effects work ok too but I don't use them. :)
2. I am pretty sure that preupgrade method is not worth trying at the moment. I did it at first. It was crash-ill but everything went smoothly to the point that it had everything installed. My problems started when anaconda told me to reboot. Fedora9 didn't boot because it couldn't find hard drives. I had also other problems with it. I don't suggest that way exept for testing what's it a like in future. And to send suggestions of course.
I didn't install livna-repo-f9 package since I thought that preupgrade/anaconda will be smart enought to update configs too. So that I can install it later and then upgrade those packages.
I suggest yum upgrade if you don't want to do clean install or download fedora9 dvd for the sake of upgrading.