Bottom line: Don't rely on the controllers to keep you out of trouble. Yes, they have very good weather radar, and, yes, they do their best to pass on weather reports and ride reports from other pilots. And, yes, they can almost always approve deviations around clouds or radar targets you see. But, when the sky fills with building thunderstorms and airplanes, controllers will at some point have to fall back to their ultimate responsibility and turn airplanes away from each other, even if that means one of them has to turn into a thunderstorm. It's their job, but it's our job to always be in a position to legally turn down that clearance.