After digging into a new army with all contrast paints save for the metal, I can confidently say that they rock. And if a color isn't quite right, a dry rush can pull it a long way towards what you're looking for with little effort.
Contrast isn't magic, and they don't solve every problem, but they do save time. They are to painting what buying gold is to MMO games. Get you to the top faster without developing your skills.
You can make incredible looking models with little effort. You can also make drippy looking trash if you overdo it.
Know that the highlights dry brighter than they look when it's wet. So, you can paint it much thinner than they suggest, so long as you're up to controlling the pooling in the shadows. Spread too many shadows around, and you get a blotchy mess. Let them get too deep and you have a drippy mess. So, you have to control how deep the shadows look, more than you 'paint'. It's like washing with an exponentially more impactful effect. (try not to have Iyanden Yellow replace all your yellow forever. I dare you.)