magic_quotes_gpc is not really considered a security feature any longer, and its use should in general be avoided.
It is deprecated since PHP 5.3.0 and will be removed all together in PHP 6.0 (see link)
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www.php.net]
Of course if you have a script, that relies on this setting for security, you should definitely turn it on, but perhaps you should also check if there are any upgrades to it.