After upgrading the lilo from latest rawhide my system hanged at the LI level. Lilo rpm writes /boot/*.b files and needs to update lilo as a part of the script.
Nope, updating boot loaders is entirely too dangerous to do as part of the %post because there is no reliable way to tell that a) the boot loader is the one in use and b) that the config file accurately reflects the state of the system.