I use this in conjuction with the P90X program and can change my weights quickly for the next exercise, allows me to maintain my cardio pace and achieve a fulfilling complete work out!
I have two pairs of 552s and one set of 1090s now. I do a set of cardio bodybuilding routines where I need 3 weight pairs to use one right after the other. These work very well for me. The only thing better would be a better sync on the weight settings. Sometimes they snag a lower or higher weight when choosing and they wont pickup. Easily fixable but a nuisance.