The MySQL 5.0.x init script is missing the ability to restart the server when it dies from a SEGV or other non-normal signal. The mysqld_safe script was written to keep the MySQL server running and will restart the server on death to maintain service reliablility, but this ability was not copied to the portage version of the init script.
There is the "/etc/init.d/mysqlmanager" script that achieve a better result, it's very simple daemon (easy to keep bug free) that launch mysqld processes. There is no possibility to copy the mysqld_safe behaviour, there is however an alternative: sys-process/daemontools, I can't tell how those integrate with current baselayout, plese ask on the forums/maillist/google for that
FWI, the refusal of using mysqld_safe made gentoo vulnerable to a mysql DoS (server crash), where most other distros were safe. security bug 171934 and http://bugs.mysql.com/bug.php?id=27513
