I won't buy a firearm without a safety; they're that ingrained in my personal manual of arms. Safety Protocol was drilled into my firearms etiquette by my father in a fashion that would make a boot instructor jealous...to the point that the times I've fired Glocks and other guns without safeties, I've felt a degree of apprehension because there was a step missing from my protocol. Draw, disengage, fire, re-engage, holster. I know perfectly well that the Glock-style trigger safety is more than sufficient to prevent an accidental discharge on a firearm with a 4 1/2 - 6 1/2 pound trigger pull, but there it is. If you hand me a "hot" firearm with a disengaged safety, I'll even go so far as to engage it myself so that I can disengage it at the proper time in my sequence.
As far as the safety on the FNS, it's the easiest and most pleasant safety I've ever worked with...neither too large nor too small, and neither disengaging too easily nor requiring so much force as to interfere with alignment if you're bringing the weapon to bear in a hurry. It simply comes off with a gentle flick of the thumb, and I've never had it change state while holstered.
(As an aside Byron, the safety isn't "filled in"...it was just never removed in the first place. The grip is the same for every FNS, whether they have a manual safety or not; the ones without just never had the cutout removed from the molded lower (though the guide lines are still visible.)