I wholeheartedly support them. I feel that my personal weapons, although I know them, may one day be manipulated by someone without that training or familiarity with my weapon. A magazine safety is reasonably unobtrusive and doesn't affect use of the weapon, while it potentially saves lives. I can pop a magazine out should I fight for it in a home-invasion scenario and render the weapon inoperable, and should a child or unresponsible adult open the case and handload a round, it still will not go off.
Miniscule benefits in trigger pull and accuracy, to me, are not worth the loss of the mag safety.