[Christ]

For the rears, you can fix the camber issues with washers behind the compensator arm (the upper "dog bone" part on the trailing arm) if you're not happy with the camber after lowering. On the front, the extra camber will help corners, and shouldn't affect straight stability at speed. It will make low-speed maneuvers a little choppy, though, because the car won't have as much steering "play" as you're used to, especially if you hyper inflate.

The camber isn't what causes funny wear on your tires, it's the toe angle. That will also cause your tires to scrub, meaning it takes more power to go the same distance. Make sure your toe is in spec, and you should be fine.

Mileage figures, I can't really help with. Some say it affects negatively unless you have some treatment under the car as well, but I don't see it working this way.