Personally I have update my fedora system from f8 to f9,and then f9 to f10 with preupgrade. Roughfully speaking,I succeed.But today when I use it to update to f10,I find something I do not like.
The main issue is that,when using preupgrade,it seems that it update to the original release of f10 without the updates rpms.So after I finish preupgrade,I also have to update lots of packages.
One accompanying issue is that,when somebody ,like me,update the system after one more month after f10 release,something bad will happen. Since I update f9 system all the time. When I update to f10 with preupgrade. One serious issue happen. A lot of f9 packages are newer than the corresponding f10 originally release packages.So the system is a "mixed" system.
Maybe next time I should consider update directly with yum.