My wife has some 15x12 Eagles on her Jeep and they have gotten scratched up pretty bad from her never washing the brake dust off them, so you'll need to wash them every couple of weeks to avoid them looking like crap. I think what happened to hers was that someone may have tried to polish them with the polishing compound that's meant for chrome plated wheels (which are much harder than aluminum) and this scratched the wheels, so then all the brake rotor dust was able to get down in the scratches and make them worse. Just something to think about.
I run 3.75" backspacing on my 15X10s and I wouldn't mind having a little less, like 3.25", maybe. Some guys have ran 2.5" backspacing before, but the wheels were sticking out so bad that they would actually hit the fenders and body even worse than if they had used wheels with too little backspacing. It's all according to the width of your wheel and what size tire you have, whether you're running inner fenders, your lift height and fender clearance, etc.
Also remember that the wider stance you get from more offset wheels could mess up your scrub radius and turning radius and all that.