I have just upgraded to 23 from 22 in a virtual machine using dnf as described in the Fedora Wiki, which went rather smoothly for me.
After manually installing the Guest Additions, the features "seemless windows" and "automatic resize of the guest desktop" don't work (the respective options in the views menu are greyed out).
The VBox kernel modules are built ok, but I get a warning saying: "unsupported pre-release version of X.Org server installed. Not
installing the X.Org drivers."
The X log says that there is X.Org X Server 126.96.36.1992 installed, which is a pre-release. I guess downgrading might cure the problem, but how?