I love 'em for tapcons in particular. I'm not a fan of the phillips-head ones, I generally use the 1/4" tapcons for anything and everything -- they're expensive, but it's nice to know they'll likely never come loose. And the magnetic aspect is great for holding materials in place with one hand while driving with the other.
PS, those freebie kits of HF screwdrivers work great for holding one end of a tapcon hole in place while you run the other end with the masonry bit. FAR easier to get things level.