There needs to be some form of error recovery in the installer, I've had three installs in a row crash durring post install config. The only way I've found out of that case is to kill off the installer and reboot the machine. Some of these are truely fatal (i.e. sending the dhcp request out the wrong eth iface) but others aren't (i.e. mounting an auxilary partition that's not part of the install, but was specified in the config, and it can't be mounted because it's busy (in actuality mounted by hand from the bash console to find the network config to avoid the dhcp issue above)). These non-fatal errors should allow a retry or skip kind of option; while the truely fatal errors should at least provide a gracefull reboot solution in the gui (for the newbies).
Adding better error handling is a continual process for the anaconda team.
Please submit individual bug reports for specific problems so we can better address them.