I installed a beta of F9 and upgraded from there (IIRC I just had to change some of the repo names from "8.92" to "9", but that could have been because I'm using Smart instead of Yum and its front-ends). There should be a preview release in a week and a bit that you might be able to wait for that will give you a smoother and smaller transition.
As for losing data, it depends what you do. If you update using PreUpgrade
then you shouldn't do. If you install F10 from CD/DVD over the top of an existing F9 install then you will lose your data if a) it isn't in its own partition (i.e. you kept /home on your / partition) or b) it is in its own partition, but you format it.