I'd recommend a clean upgrade if making a jump that large because there are huge differences between the 2 versions of Fedora. Create a tar of your /etc directory and put it somewhere in /home before backing up. I'd also reccommend an inventory of what you have installed. (rpm -qil > ~/FC6_list.txt) so you can easily reference anything you're missing. Also, if you're upgrading from that far back, I'd have to ask if you have enough ram to successfully run FC12. I'd recommend at least a GB so you can avoid swapping.
Then again, if you're happy with FC6, and it does everything you want it to do, upgrading isn't mandatory, so you're free to stay with what works for you.
Thanks for the advice. I wasn’t really contemplating FC6->FC12 as in something I was going to do this weekend.
More just the idea of the best way to go about it in general.
I like the idea of tarring /etc and the rpm command you gave me (although sometimes I build from source and then make install - that wouldn’t help me there, would it?)