I cant' comment on how the wiring performs with typical single coil pickups (as used in the Legacy). With my G&L Comanche, which has Z-coils as opposed to traditional Strat-style single coils, it's a great system.

AFAIK, the Zs are parallel-wired humbuckers along the lines of a P Bass pickup. They offer a very full sound across the spectrum - nice highs and a HUGE bottom. With the controls maxed, you get a sound that has more overall output and bass response than a typical Strat (great for driving pedals!). This is where the G&L wiring comes in handy. Since there seems to be so much to work with, it's handy to remove a bit here and there (a little nip and tuck if you will) to tailor your tone. (e.g. roll back the bass about halfway and roll back the volume a tad and you venture back into traditional Strat territory).

Depending on what pickups you use, the wiring can be highly useful. I suppose it can be very handy for pickups that offer a little more mid-low and low end meat than typical Strat singles (i.e. 290s, 490s, 495s, maybe even 250s, etc.).

BTW, the G&L 7-way system (on Comanches, S-500s and maybe Legacies???) can be addicting as well.