My Ibanez came with quantum pickups the QM1, S1 and QM2 - which isn't what yours came with is it?
Anyway the nailbomb added a lot of clarity, definition, articulation, but i wouldn't say it tightened up the sound at all. The Quantum pups are ceramic as far as i know, so werealready very tight. The Nailbomb has a far stronger midrange, which really brings out the best in the S, and like pagan said - made it Incredibly versatile. It's like it's added a third dimension to my now FAVOURITE guitar.