I'm not a fan of using anything magnetized inside my PC. Others will swear up and down that it's not a problem, but I just don't take the risk. (Same thing with using an anti-static band.)
If your screwdriver is the right size, it will often "grip" the screw long enough to get it in place, I've found. Also, *tiny* drop of white glue (like Elmers) on the screwhead for getting into really tight spots works.