there was a big debat on pirate4x4 a while ago.  i'm running the sky's kit and like it.  one thing i like is that the spacer only sees braking loads where a wheel spacer would see braking, acceleration, turning, and side load forces.  so i feel better that they see less loads.  but there are advantages to the wheel spacers, cheaper and quicker to install and you don't have to have ifs hubsl.  the sky kit was a bit of a pain in the arss to install.  we had trouble lining up the spacer when pressing it on to the hub the first time.  the second one i made a guide pin out of a bolt with the head cut off and then made sure to pollished all the rust and crap off the surface of the hub where the spacer presses on, used a bit of white grease and it went right together.  the one thing i don't like it that you would have to press the rotor off to replace it... not a big deal as i don't plan on haveing to change rotors all that often.